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©OPXMGHT DEPOSIT. 



Electrical Tables and 
Engineering Data 

A Book of Useful Tables and Practical Hints 
for Electricians, Foremen, Salesmen, Solici- 
tors, Estimators, Contractors, Archi- 
tects and Engineers 

By 
HENRY C. HORSTMANN 

and 

VICTOR H. TOUSLEY 

Authors of 

" Modern Wiring Diagrams," " Modern Electrical Con- 
struction," "Practical Armature and Magnet Wind- 
ing," "Electrician's Operating and Testing 
Manual," "Modern Illumination, Theory 
and Practice," "Alternating Cur- 
rent," "Motion Picture Oper- 
ation, Stage Electrics 
and Illusions." 



ILLUSTRATED 



CHICAGO 

FREDERICK J. DRAKE & CO. 

Publishers 



T!T 



isi 






Copyright 1920 and 1916 

by 

Henry C. Horstmann and Victor H. Tousley 



^o 






5> 



JUL -I 1920 
©CI.A570540 



PREFACE 

This book is an attempt to furnish electricians 
generally and I others interested in electrical work 
with a reference and table book which can be con- 
veniently carried in the pocket. It contains no theo- 
retical discussions. Its scope is limited to practical 
information which is daily called for but , seldom 
available at the time most needed. The matter is 
arranged in alphabetical order which enables one 
to find any item with a minimum of delay. 

The tables provided assist in the calculation of al- 
most every conceivable problem with which con- 
struction men have to deal, and by their use many 
hours of tedious calculations may be avoided. 

THE AUTHORS. 



ELECTRICAL TABLES AND 
ENGINEERING DATA 



Acid Fumes. — In places where acid fumes or cor- 
rosive vapors may exist, the nature of the vapors 
will determine the insulation to be used. Consult 
chemists and Inspection Department having juris- 
diction. Conduit work is not favored much in such 
places, but if it can be shown that the vapors in 
question are not harmful to the metal it is permissi- 
ble. 

Adapters. — There is no objection to the use of 
adapters, provided they are of approved type. 

Adjusters. — The use of cord adjusters should be 
discouraged, but there is no very serious objection to 
the use of any that do not severely damage the cord. 

Air Compressors. — Air compressors are usually 
driven by series wound motors and made to stop 
and start automatically. For a. e. work induction 
motors are used. Tanks should be of a capacity 
equal to about 50 per cent of the rated capacity of 
the compressor per minute. The air should be dry 
and cool, as most of the moisture will be precipi- 
tated. One H.P. will compress about 5% cu. ft. of 
free air per minute to 90 lbs. 

Alternating Current Wiring. — For alternating cur- 
rent systems the two or more wires must be run in 
the same metal conduit, armored cable or metal 
moulding. In open wiring the greater the separa- 
tion of wires, the greater will be the inductive drop. 
7 



8 ELECTRICAL TABLES AND DATA 

See also special tables for sizes of motor wires anu 
wiring systems. 

Alternators. — Alternating current generators and 
their exciters are not usually provided with fuse 
protection. 

Aluminum. — Aluminum is used as a rule only for 
outside work and for bus-bars. It can be soldered, 
but soldering is more difficult than with copper wire 
and clamps are therefore much used. When used 
for bus-bars the current density ranges from 1,000 
to 1,200 amperes per sq. in. for the smaller sizes, and 
about 500 for the heavy bars. See Bus-Bars for 
table. For insulated aluminum wire the safe carry- 
ing capacity is 84 per cent of that given for copper 
wire of same insulation. Aluminum is electroposi- 
tive and must be tied with aluminum wire and nc 
other metal must be allowed to touch it. 

Comparison of Copper and Aluminum : 

Aluminum Copper 

Specific gravity 2.68 8.93 

Eelative specific gravity 1.00 . 3.33 

Conductivity 61 to 63 96 to 99 

Weight for equal area 47 100 

Area for equal conductivity 160 100 

Diameter for equal conductivity. 126 100 

It will be noted that an aluminum wire of equal 
conductivity is about two sizes larger by B. & S. 
gauge than a copper wire. The tensile strength of 
aluminum is from 20,000 to 35,000 pounds per square 
inch; that of copper from 20,000 to 65,000. For 
carrying capacity, etc., see Wire Calculations. 

Ammeters. — It is customary to provide an ammeter 
for each generator connected to a switchboard, and 
only the very smallest and cheapest boards are ever 
put up without one. The cord sent out with shunt 
ammeters must always be used full length and need 
not be protected by fuses. Never place an ammeter 






ELECTRICAL TABLES AND DATA 9 

in any lead that can be affected by equalizer current. 
An ammeter used for battery charging should indi- 
cate direction of current. 

Ampere's Rule. — Imagine yourself swimming with 
the current and facing the center of the coil; the 
left hand will then point toward the north pole of 
the magnet. 

Anode. — The anode is the positive pole. 

Annunciators. — Unless the annunciator is known 
to be especially constructed for high voltage, no at- 
tempt should be made to operate it from light or' 
power circuits. Use bell ringing transformers, mo- 
tor generators or battery. Annunciators cannot be 
operated in parallel successfully. 

Apartment Buildings. — If practicable, meters 
should be placed in basement. In some cities spe- 
cial rules for the wiring of apartment buildings ex- 
ist. No cut-outs should ever be placed in closets; 
place them in kitchen if possible. To determine ap- 
proximate size of mains necessary to supply lighting 
in apartment buildings, estimate one watt per square 
foot and consult table of carrying capacities. 

Arcades. — The illumination of arcades should be 
kept low so as not to interfere with show windows. 

Arc Lamps. — In laying out wiring for arc lamps 
the question of drop need not be considered unless 
incandescent lamps are also on the circuit. A wire 
smaller than No. 6 should not be used for theatre, or 
moving picture arc lamps. Two dissolving stereop- 
ticon lamps are usually rated as about equal to one 
stage or moving picture arc lamp. 

Plugs used for arc and incandescent lamps should 
not be interchangeable. The light from direct cur- 
rent arc lamps is much better than that from alter- 
nating current. Series arc lamps are now operated 
almost entirely from constant current transformers; 
each transformer being limited to one circuit. 



10 



ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 1£ 

Armored Cable and Cord. — Armored conductors 
are very suitable for "fish work." The radius of 
the curve of the inner edge of anj^ bend must not be 
less than iy 2 inches. "Where moisture exists the con- 
ductors should be lead-covered under the armor. Ar- 
mored cable is not nail proof under- all circumstances.. 

TABLE I 

Outside Diameters of Armored Cables and Weight Per 100 Ft. 
Greenfield Flexible, Steel Armored Conductors 







Solid 




Stranded 






Dia. 


Wt. 




Dia. 


Wt. 


B& 


in. 


lbs.: 


B&S 


in. 


lbs. 


Single conductors, type D. 


.14 


.37S 


20 


10 


.450 


23 




12 


.384 


21* 


8 


.469 


28 




10 


.434 


26 


6 


.631 


54 




8 


.464 


28 


4 


.717 


63 




6 


.609 


54 


2 
1 


.783 
.900 


71 

98 


Twin conductors, BX 


.14 


.630 


45 


8 


.830 


77£ 




12 


.670 


48 


6 


1.1-16 


121 




10 


.720 


54 


4 


1.203 


143 


Three conductors, BX3... 


.14 


.675 


53 


8 


.890 


93 




12 


.715 


561 


6 


1.144 


153 




10 


.785 


66 








Single conductors, DL .... 








10 
8 


.506 
.564 


53 

72 


Lead covered, and steel 








6 

4 


.713 

.780 


95 
110 


armored 








2 
1 


.825 
.897 


125 




165 


Twin conductors, BXL... 


.14 


.730 


68 


8 


.978 


136 


Steel armored and lead 


12 


.758 


78 


6 


1.152 


205 


covered 


.10 
.14 


.863 

.782 


110 

78 


8 


1.056 




Three conductors, BXL3 , . 


164 


Lead covered and steel 


12 


.815 


97 








armored 


.10 


.933 


129 


18 


.414 




Steel armored, flexible- 


20 


cord, Type E 








16 


.447 


22 










14 


.625 


38 


Steel armored, flexible re- 






18 


.530 


25 


inforced cord, Type EM. 








16 
14 


.540 
.652 


26 

48' 



12 ELECTRICAL TABLES AND DATA 

Armory. — Armories are often classed with thea- 
tres and assembly halls, and must be wired accord- 
ingly. The most important part of an armory is the 
drill hall. This requires an illumination equal to 
about two or two and one-half foot candles. This 
is best obtained by placing large units high up out 
of the range of vision. 

Artists. — Require an adjustable light and pendant 
drops are most serviceable. 

Art Gallery. — Art galleries are also often classed 
with assembly halls. In illuminating statuary, the 
aim must be to produce some shadow effect because 
of the uniformity of color. Lights should be hung 
high. For white statuary an illumination of two- 
foot candles will be sufficient; for bronze statuary 
about four times as much should be provided. Paint- 
ings are often illuminated by strips and reflectors, 
and also by indirect lighting or Holophane globes. 
As many paintings must be viewed from a distance, 
a bright illumination of about five foot candles is 
recommended. 

Asbestos. — This becomes a conductor when wet, 
and must not be used in damp places. Asbestosless 
than -J inch thick is not considered serviceable. ' As- 
bestos covered wires are much used for connecting 
arc lamps and rheostats where the wire is subject to 
much heat. 

Assembly Halls. — The National Electrical Code 
prescribes that if any part of a building is "regu-" 
larly or frequently used for dramatic, operatic, 
moving picture, or other performances or shows, or 
has a stage used for such performances used with 
scenery or other stage appliances, ' ' it must be classed 
as a theatre, and wired according to theatre rules. 
It is usual to specify that all wires must be in con- 
duit and that there must be a separate system of 
lighting, independent of the main system, for use of 



ELECTRICAL TABLES AND DATA 13- 

the audience in leaving the building in case of fire,, 
or other emergency. 

Attachment Plugs. — Must be of approved type. 
They should be of the pull-out type, and the socket 
so placed that the plug can pull out in case strain is; 
put upon it. 

Automatic Cut-outs are required to protect every 
device, or wire, which is connected to any power 
circuit, except alternators and constant current 
generators. For details see Cut-outs. 

Automobiles. — In wiring automobiles it is custom- 
ary to disregard all ordinary construction rules. 
Electric motors are connected without any fuse pro- 
tection. A fuse blowing on a heavy up-grade might 
cause disaster. 

Auto-Starters. — As a general rule, auto-starters are 
not used with motors smaller than 5 H.P. Auto 
starters provided with overload release devices, and 
so arranged that the handle cannot be left in the 
starting position, are obtainable and should be used. 
Small auto-starters have usually three taps, and these 
are arranged to give about 50, 65 or 80 per cent of 
the line voltage. Larger starters usually have four 
taps arranged respectively for 40, 58, 70 and 80 per 
cent of the line voltage. Always make connections. 
to the lowest voltage tap that will give the necessary 
starting torque. Wherever possible, place starter in 
sight of motor. For motors smaller than 5 H.P., 
throw-over switches are often used. 

Bakeries. — In bakeries, hot places will be found in 
which rubber-covered wire is not suitable. 

Balance Sets. — Balance sets are made up of motor 
generators or transformers, and exist for the pur- 
pose of obtaining a neutral wire and low voltage 
for a small lighting load operated in connection with 
a higher voltage two-wire generator. They are also 
used where motors operate at two voltages. The 



14 ELECTRICAL TABLES AND DATA 

capacity of a balancing set is usually only a small 
percentage of the total load. 

Balancing". — Three-wire systems are usually ar- 
ranged so that a minimum of current may pass 
through the neutral wire. A good balance cannot 
always be obtained, and in some cases considerable 
judgment is required to determine which is the best 
arrangement of apparatus. Three wires should be 
carried to every center supplying more than one 
circuit. Safety rules require the neutral wire to be 
of same size as the outside wire, but in large systems 
this wire will seldom be called upon to carry more 
than 10 per cent of the current used at any time. 

Ball Rooms. — Ball rooms are often classed with 
theatres. The illumination should be general, and 
lamps hung high. A general illumination of from 
two to four foot candles is recommended. Recep- 
tacles for musicians' use should be provided. 

Banana Cellars. — These places are always hot and 
moist and the vapors are very corrosive. Conduits 
corrode very fast, and especially the small screws 
in outlet boxes ; brass screws are often used. Open 
wiring, if it can be protected, is preferable. 

Banks. — In that part of a bank occupied by the 
clerical force, a general illumination of from three 
to four foot candles is recommended. These lights 
are in use most of the time, and high efficiency lamps 
should be arranged for. In that portion used by the 
public the illumination is not so much used, and 
may be of a lower order. Numerous outlets for 
adding machines and fan motors should be provided. 
In some banks the private depositors' rooms are 
fitted with two lights, one above and one below 
desks, and provided with three-way switches so that 
only one light can be used at a time; this for con- 
venience of customers who may have dropped things 
on the floor. 



ELECTRICAL TABLES AND DATA 15 

Barber Shops. — Good illumination of barber shops 
can be arranged for by placing clusters of fairly 
large candlepower close to the ceiling and a little 
to the rear of chairs. Placed in this manner, the 
light will not be forced directly into the line of 
vision of the customer, and yet give the desired 
illumination. The mirrors in front of chairs will 
reflect much of the light back to the chair. Often 
lights are placed along the mirrors, but this practice 
is not to be recommended. Outlets for cigar-lighters, 
curling-iron heaters, vibrators, etc., will be appre- 
ciated. 

Barns. — The use of brass shell sockets should be 
avoided in horse barns. Avoid placing lights in 
front of horses, and keep all lights well up above 
horses' heads. Use weatherproof construction in 
wash rooms. Place lights in all dark corners. 

Bases. — All electrical contacts must be mounted on 
non-combustible, non-absorbtive insulating material. 
Other materials than slate, marble, or porcelain are 
not favored much, and are allowed only when the 
first named are too brittle. Sub-bases are generally 
provided for all switches and other devices which 
would otherwise allow the wires to come against 
wood or plaster. 

Base Frames, — Base frames are required under all 
generators and motors, and where the voltage is not 
in excess of 550 volts it is customary to use insulated 
base frames. If the motor operates at a voltage in 
excess of 550, it is better to ground the frame thor- 
oughly. Where frames cannot be insulated they 
must be grounded. 

Basements. — Basements are often damp, and must 
then be wired in accordance with rules for such 
places. As ceilings are usually low, protection 
against mechanical injury is often necessary. 



16 ELECTRICAL TABLES AND DATA 

Batteries, Primary. — Dry batteries are much used 
at the present time. They require no attention and 
when worn out are simply thrown away. The dry 
battery is at present made only for open circuit 
work. The wet battery used mostly for open circuit 
work consists of carbon and zinc elements immersed 
in a solution of sal-ammoniac. The carbon is the 
positive pole. This battery is charged by dissolving 
about four ounces of sal-ammoniac in sufficient water 
to fill the jar about three-fourths full. Never use 
more sal-ammoniac than will readily dissolve. It is 
preferable to make a saturated solution and, after 
filtering it through cloth, to add about 10 per cent 
of water. Keep jars in a cool place to prevent evapo- 
ration. Never allow water to freeze. Keep exposed 
parts covered with paraffine. Do not allow battery 
to be short circuited or run down. If this has oc- 
curred, it will often pick up if left on open circuit 
for a few hours. If the solution appears milky, 
more sal-ammoniac is required. Impure zincs which 
do not eat away evenly facilitate the formation of 
crystals which greatly increase the resistance. The 
best known of the closed circuit batteries is the 
gravity type. The elements in this cell are zinc and 
copper, immersed in a solution of sulphate of copper 
(blue vitriol). The copper element rests on the bot- 
tom of the jar, and the blue vitriol is placed around 
it and the jar filled with clean water. The cell must 
be short circuited for a few hours to start the action. 
The blue solution should rise to about midway be- 
tween the two elements. This cell must be kept in 
action or it will rapidly deteriorate. 

Connect all batteries so that the resistance of the 
battery is nearest equal to the resistance of the de- 
vices it is to operate. Series connection should be 
used when the external resistance is higher than the 
internal battery resistance. If the external resist- 



ELECTRICAL TABLES AND DATA 17 

ance is lower than that of the battery, group cells 
in multiple. When arranging small storage batteries 
to be charged from lighting or power circuits, pro- 
vide double throw switches to entirely disconnect 
battery from power circuit while it is on the bell 
circuit. Install all wiring subject to power voltage 
in accordance with rules for that voltage. 

Batteries, Secondary. — Small storage batteries- 
may be carried about and used. The larger ones 
must remain stationary and are used as compensa- 
tors for feeder drop, equalizers on three-wire sys- 
tems, preventives against shut down and as a com- 
bination of all of these. Medium size storage 
batteries are also much used with automobiles. All 
storage batteries with exception of the Edison, use 
lead plates. The active material is sponge lead im- 
mersed in a weak solution of sulphuric acid. The 
positive plates when fully charged are of a chocolate 
color and the active material is quite solid. The 
negative plate is more of a slate color and softer. 
The unit of capacity is the ampere hour. A 60- 
ampere-hour battery, for instance, can deliver a cur- 
rent of three amperes for twenty hours, or seven 
and one-half amperes for eight hours. High voltages 
are obtained by connecting a number of cells in 
series. High amperage is obtained by connecting . 
plates in parallel. The voltage is independent of 
the size of the cell, but the amperage capacity varies 
with the surface of the opposed plates. The effi- 
ciency is roughly about 75 per cent. The safe rate 
of charge and discharge varies from five to ten am- 
peres per square foot of positive plate surface, both 
sides of plate being measured. The voltage should 
never be allowed to fall below 1.8, and when fully 
charged is about 2.6. The condition of full charge 
is indicated by both the positive and negative plates, 
gassing freely. 



18 ELECTRICAL TABLES AND DATA 

Before manipulating or attempting to connect any 
storage battery, the instructions of the maker should 
be obtained. The following instructions form only 
a general guide : Keep electrolyte well above plates. 
See that the cells are kept clean and allow nothing 
that could short-circuit the plates to accumulate at 
the bottom. Keep whatever separators there may be 
in place. Allow no metal except lead in the battery 
room. Insulate cells from ground and from each 
other. See that battery is recharged as soon as pos- 
sible after being used. Do not overcharge. When 
the negative plates begin to give off gas, it is time 
to quit. Never allow the voltage to fall below 1.75 
per cell. The temperature of the battery should not 
rise above 110 degrees. The capacity of battery 
needed is governed by number of units in the gen- 
erating plant. It is not likely that more than one 
unit will give out at a time. 

Bells. — Bell-ringing transformers are much used in 
connection with alternating current in place of bat- 
teries. To operate bells in series, jump circuit 
breaker on all but one. If bells are to be operated 
from lighting circuits, the wiring must be installed 
in accordance with rules for the voltage used, and 
the bell must be specially approved for that service. 
The chief hazard that exists with low voltage bell 
wires is the possibility of coming in contact with 
other wires. If storage batteries of high amperage 
capacity are used, the wires should have fuse 
protection. 

Belting. — Figure 1 is an illustration of a service- 
able method of belt lacing. Thread lacing from left 
to right according to heavy lines, double up at ends 
and return to starting point; cross lacing on out- 
side of belt only, and keep laces on inside parallel 
with length of belt. 






ELECTRICAL TABLES AND DATA 19 

Holes should be punched as nearly as possible 
according to the following table : 



TABLE II 

Width of Belt 

2 to 6 to 12 to 18 to 

Distance from edge of belt — 6 in. 12 in. 18 in. 24 in. 

First row i f ,| 1 

First row i f | 1 

Second row. £ 1 1£ 1§ 

Second row 1 1^ 1J 2 

Distance apart of each row of holes 1 1J 1| 2 

Size of lace leather T 3 s i f J 

If pulleys are of same size, or far apart if of 
different sizes, the length of belt can be quite approx- 
imately found by the following rule : Add diameters 




Figure 1. — Method of Belt Lacing. 

of pulleys and multiply by 1.57 ; to this add 2 times 
the center-to-center distance. The length of belting 
contained in a roll can be found by reference to 
Table III. Multiply number of layers in roll by 
number found where outside diameter of roll and 
diameter of hole in center cross. 

Example. — A roll of belting of 48 inches outside 
diameter has a hole in the center six inches in diam- 



20 ELECTRICAL TABLES AND DATA 

eter, and there are 88 layers of belting. Where the 
line pertaining to 48 inches outside diameter crosses 
the line pertaining to 6-inch hole, we find the num- 
ber 7.04, which multiplied by 88 gives 619.52 feet 
of belting. The width of a single belt necessary to 
perform a certain amount of work can be found by 
the formula W = 1200xH.P.-rF, where W stands for 
width, H.P. for horsepower, and V for velocity of 
belt in feet per minute. This formula will give a 
belt of ample size, and a smaller one can be made 
to do the work by giving it greater tension. Table 
IV is calculated from the above formula and shows 
the capacity of belts of various widths and operating 
at various velocities. 

Belts should run horizontally and the pull should 
be on the under side. Tightener should be on slack 
side and close to main pulley. Belts running ver- 
tically must be kept very tight, especially if the 
lower pulley is small. The proportion between two 
pulleys close together should not be greater than 
6 to 1. Double belting should not be used on pulleys 
less than 3 feet in diameter. Rubber belting is pref- 
erable in damp places. Thin belting is best for high 
speeds. Belts operating at high speeds should be 
cemented, not laced. Pulleys should be perfectly 
smooth. 

Billboards. — A very bright illumination of from 
ten to twenty foot candles is often used. Lights 
must be encased in reflectors so as not to be visible 
to the observer. Install wiring according to rules 
for outside work. 

Billiard Halls. — A general illumination of about 
one foot candle is recommended. Above each table 
there should be an illumination of four or five-foot 
candles. The light over the table should be uniform. 
At least two lamps should be provided for each 
table, and should be so encased that the lights are 



ELECTRICAL TABLES AND DATA 21 

TABLE III 

Table for Calculating Length of Belting, Eope or Wire in Coils 



Outside i Diameter of Hole in Inches > 

Diameter 2 3 4 5 6 7 8 9 10 11 12 



6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
22 
24 
26 
28 
30 
32 
34 
36 
38 
40 
42 
44 
46 



...1.05 1.17 1.30 1.44 

...1.17 1.31 1.44 1.57 1.70 

...1.31 1.44 1.57 1.70 1.83 1.96 

...1.44 1.57 1.70 1.83 1.96 2.09 2.23 

...1.57 1.70 1.83 1.96 2.09 2.23 2.46 2.49 

...1.70 1.83 1.96 2.09 2.23 2.36 2.49 2.62 2.75 

...1.83 1.96 2.09 2.23 2.36 2.49 2.62 2.75 2.8.8 3.01 

...1.96 2.09 2.23 2.36 2.49 2.62 2.75 2.88 3.01 3.14 3.27 

...2.09 2.23 2.36 2.49 2.62 2.75 2.88 3.01 3.14 3.27 3.40 

...2.23 2.36 2.49 2.62 2.75 2.88 3.01 3.14 3.27 3.40 3.53 

...2.36 2.49 2.62 2.75 2.88 3.01 3.14 3.27 3.40 3.53 3.66 

...2.49 2.62 2.75 2.88 3.01 3.14 3.27 3.40 3.53 3.66 3.79 

...2.62 2.75 2.88 3.01 3.14 3.27 3.40 3.53 3.66 3.79 3.92 

...2.75 2.SS 3.01 3.14 3.27 3.40 3.53 3.66 3.79 3.92 4.06 

...2.88 3.01 3.14 3.27 3.40 3.53 3.66 3.79 3.93 4.06 4.19 

...3.14 3.27 3.40 3.53 3.66 3.79 3.92 4.05 4.19 4.32 4.45 

...3.40 3.53 3.66 3.79 3.92 4.05 4.19 4.31 4.45 4.58 4.72 

...3.66 3.79 3.92 4.05 4.18 4.31 4.45 4.57 4.71 4.84 4.97 

...3.92 4.05 4.18 4.31 4.44 4.57 4.71 4.83 4.98 5.11 5.24 

...4.18 4.31 4.44 4.57 4.70 4.83 4.98 5.09 5.23 5.36 5.50 

...4.44 4.57 4.70 4.83 4.96 5.09 5.24 5.35 5.49 5.62 5.75 

...4.70 4.83 4.96 5.09 5.22 5.35 5.50 5.62 5.75 5.88 6.01 

...4.96 5.09 5.22 5.35 5.48 5.67 5.76 5.88 6.02 6.15 6.28 

...5.22 5.35 5.48 5.61 5.74 5.88 6.02 6.14 6.28 6.41 6.54 

...5.48 5.61 5.74 5.87 6.00 6.14 6.28 6.41 6.57 6.68 6.82 

...5.74 5.87 6.00 6.13 6.26 6.40 6.54 6.67 6.81 6.94 7.08 

...6.00 6.13 6.26 6.39 6.52 6.66 6.80 6.93 7.07 7.20 7.34 

...6.26 6.39 6.52 6.65 6.78 6.92 7.06 7.19 7.33 7.46 7.60 

...6.52 6.65 6.78 6.91 7.04 7.18 7.32 7.45 7.56 7.72 7.86 



This table may also be used to estimate length of 
rope or wires in coils if number of turns can be 
determined. 



ELECTRICAL TABLES AND DATA 



TABLE IV 

The table below is calculated from the above formula and 
shows the number of H. P. belts will transmit 



Belt Speed 




















in Ft 


n. r ~ 




i 


fVidtr 


of Belt in Inches — 






Per Mi 










1 


2 





4 


5 


6 


7 


8 


9 


10 


200 . 


. . .16 


.33 


.50 


.66 


.83 


1.00 


1.16 


1.33 


1.50 


1.66 


300 . 


. . .25 


.50 


.75 


1.00 


1.25 


1.50 


1.75 


2.00 


2.25 


2.50 


400 . 


. . .33 


.66 


1.00 


1.32 


1.66 


2.00 


2.33 


2.66 


3.00 


3.32 


500 . 


. . .42 


.84 


1.25 


1.67 


2.10 


2.50 


2.95 


3.34 


3.75 


4.20 


600 . 


. . .50 


1.00 


1.50 


2.00 


2.50 


3.00 


3.50 


4.00 


4.50 


5.00 


700 . 


. . .58 


1.14 


1.75 


2.33 


2.90 


3.42 


4.08 


4.67 


5.25 


5.80 


800 . 


. . .67 


1.34 


2.01 


2.66 


3.34 


4.02 


4.67 


5.33 


6.00 


6.68 


900 . 


. . .75 


1.50 


2.25 


3.00 


3.75 


4.50 


5.25 


6.00 


6.75 


7.50 


1000 . 


. . .83 


1.66 


2.49 


3.33 


4.15 


4.98 


5.83 


6.66 


7.50 


8.30 


1200 . 


..1.00 


2.00 


3.00 


4.00 


5.00 


6.00 


7.00 


8.00 


9.00 10.0 


1400 . 


..1.16 


2.32 


3.50 


4.67 


5.80 


7.00 


8.13 


9.3410.5 


11.6 


1600 . 


..1.33 


2.66 


4.00 


5.33 


6.66 


8.00 


9.33 10.6 


12.0 


13.3 


1800 . 


..1.50 


3.00 


4.50 


6.00 


"7.50 


9.00 10.5 


12.0 


13.5 


15.0 


2000 . 


..1.67 


3.34 


5.00 


6.67 


8.36 10.0 


11.7 


13.4 


15.0 


16.7 


2200 . 


..1.83 


3.66 


5.50 


7.32 


9.15 11.0 


12.8 


14.6 


16.5 


18.3 


2400 . 


..2.00 


4.00 


6.00 


8.00 10.0 


12.0 


14.0 


16.0 


18.0 


20.0 


2600 : 


..2.16 


4.32 


6.50 


8.66 10.8 


13.0 


15.1 


17.3 


19.5 


21.6 


2300 . 


..2.33 


4.66 


7.00 


9.33 11.6 


14.0 


16.3 


18.6 


21.0 


23.2 


3000 . 


..2.50 


5.00 


7.50 10.0 


12.5 


15.0 


17.5 


20.0' 


22.5 


25.0 


3200 . 


..2.66 


5.32 


8.0010.6 


13.3 


16.0 


18.6 


21.2 


24.0 


26.7 


3400 . 


..2.83 


5.66 


8.50 11.3 


14.1 


17.0 


19.8 


22.6 


25.5 


28.2 


3600 . 


..3.00 


6.00 


9.00 12.0 


15.0 


18.0 


21.0 


24.0 


27.0 


30.0 


3800 . 


..3.16 


6.32 


9.50 12.6 


15.8 


19.0 


22.1 


25.2 


28.5 


31.6 


4000 T 


..3.33 


6.66 10.0 


13.3 


16.6 


20.0 


23.3 


26.6 


30.0 


33.2 


4200 . 


..3.50 


7.00 10.5 


14.0 


17.5 


21.0 


24.5 


28.0 


31.5 


35.0 


4400 . 


..3.67 


7.34 11.0 


14.6 


18.3 


22.0 


25.6 


29.2 


33.0 


36.6 


4600 . 


..3.83 


7.6611.5 


15.3 


19.1 


23.0 


26.8 


30.6 


34.5 


38.2 


4800 . 


..4.00 


8.0012.0 


16.0 


20.0 


24.0 


28.0 


32.0 


36.0 


40.0 


5000- . 


..4.17 


8.34 12.5 


16.7 


20.9 


25.0 


29.2 


33.4 


37.5 


41.8 



ELECTRICAL TABLES AND DATA 



TABLE V 

Table showing approximate lengths of material which must 
be cut out of belts to double the tension; sag on upper and 
lower sides assumed equal. Eeducing sag by one-half- ap- 
proximately doubles the tension. 

Distance Between 
Pulley Centers 

in Feet t Dimensions Below in 64th of an Inch \ 

4— Sag 31 46 62 77 92 108 123 138 154 

Cutout 2 3 5 7 10 13 17 20 

6— Sag 46 69 92 115 138 161 184 207 231 

. Cutout ... 1 3 5 7 11 15 19 25 30 

8— Sag 62 92 123 154 185 216 246 277 308 

Cutout ... 1 4 6 10 15 20 26 33 41 

10— Sag 77 115 154 192 230 269 307 346 384 

Cutout ... 1 4 8 12 18 25 32 41 50 

12— Sag 92 138 184 230 276 322 368 415 462 

Cutout ... 2 5 9 14 21 29 38 49 59 

15— Sag 115 173 231 288 345 402 459 518 577 

Cutout ... 2 7 12 18 28 37 48 62 76 

l S _Sag 138 207 277 346 415 485 554 623 693 

Cutout ... 3 8 14 22 33 44 58 74 91 

21— Sag 161 242 323 404 485 566 647 727 807 

Cutout ... 3 9 16 26 39 51 70 87 106 

25— Sag 192 288 384 480 576 672 768 864 960 

Cutout ... 4 12 19 31 46 61 SI 104 127 

30— Sag 231 346 461 576 691 806 9211036 1151 

Cutout ... 4 14 23 37 55 74 97 124 152 

The above table is based upon the ratio of deflec- 
tion and elongation of wires in spans, and it is 
assumed that the additional strain produces no 
immediate elongation of the belt. 



24 ELECTRICAL TABLES AND DATA 

not visible to the players. A switch for each table 
will be a convenience. Outlets for cigar-lighters 
and fan motors should be provided. 

Bonds. — Rail bonds should not be smaller than 
No. 000. The area of contact should be about eight 
times the cross section of the bond. In some in- 
stances the size of bond is determined by the size of 
supply wires, the total cross section of all bonds at 
any point being made equal to the cross section of 
the supply wires for that point. For a ratio of 1 : 12 
the copper in circular mils necessary to equal the 
conductivity of steel rails can be found by multiply- 
ing the weight per yard of rail by 10,000. 

Boosters. — Boosters may be in the form of trans- 
formers or motor generators, and are used to raise 
or lower voltage, also in some cases in return rail- 
way circuits to lessen electrolysis. The installation 
of boosters is not profitable except on long lines 
when the cost of copper to prevent the drop is 
greater than the cost of boosters. Boosters may be 
compounded so that the regulation becomes auto- 
matic. 

Bowling Alleys. — The illumination should be ar- 
ranged so that no light is visible to the players. An 
illumination equal to one and one-half or two foot 
candles is advisable for the alley, and about double 
that much for the pins. 

Branch Blocks must always provide double pole 
fuse protection for each circuit. 

Branch Circuits. — The term, " branch circuit," is 
here used to describe that part of the wiring between 
the last fuse and the lights, motors, heaters, or other 
translating devices. Branch circuits should be 
grouped as far as possible and arranged so that the 
cut-out cabinet may be in a safe and convenient 
place. It is advisable to place the switches outside 
of cut-out cabinets. In the best arranged theatres 



ELECTRICAL TABLES AND DATA 25 

all -branch circuits, except those for emergency 
lights, are carried to stage switchboards. By run- 
ning mains as far as possible, and shortening the 
branch circuits, a much evener voltage at lamps will 
be secured than is possible from long branch cir- 
cuits. The drop in voltage should never be over 2 
per cent. Most lamps are marked for three voltages, 
top, middle, and bottom, and there is a difference of 
four volts between them. "With a 4 per cent drop a 
110-volt lamp will be at different times subject to all 
three voltages and the illumination will vary greatly. 
For best location of cut-outs, see table on calcu- 
lation of materials. The following table shows drop 
in voltage with different wires at different distances. 
A run of No. 14 wire 110 feet long feeding twelve 
lights evenly spaced ten feet apart will cause a drop 
of about one and one-quarter volts between first and 
last lamps. The table below shows the drop with 
wires from No. 14 to 6, carrying six amperes the 
distances gtiven at top of table. 







TABLE VI 














Distance in feet; one 1 


e g 








B & S 


20 


40 60 80' 100 120 


140 


160 


180 


200 


14 .. 


.63 


1.3 1.9 2.5 3.2 3.8 


4.4 


5.0 


5.7 


6.3 


12 .. 


.40 


.80 1.2 l.G 2.0 2.4 


2.8 


3.2 


3.6 


4.0 


10 .. 


.25 


.50 .75 1.0 1.3 1.5 


1.8 


2.0 


2.3 


2.5 


8 .. 


.15 


.30 .45 .60 .75 .90 


1.1 


1.2 


1.4 


1.5 


6 .. 


.10 


.20 .30 .40 .50 .60 


.70 


.80 


.90 


1.0 



Burglar Alarm. — A good burglar alarm is one 
so wired that it is under constant test, so as to give 
immediate notice when any part of it is out of order. 
The closed circuit system complies with this require- 
ment. With open circuit systems it is best to pro- 
vide " silent test" by which it can be tried out every 
night without causing an alarm. To guard against 
purposive incapacitating, some installations are 



26 ELECTRICAL TABLES AND DATA 

mixed open and closed circuit system, so that it is 
impossible to know which wire to cut or short-circuit 
in order to prevent an alarm. In some systems 
"balanced" relays are used and the wires are inter- 
woven so that it is impossible to interfere with them 
in any way without giving an alarm. "Where either 
the simple open or closed circuit system is used, the 
wires and batteries should be protected against inter- 
ference. 

Bus-Bars. — The term, "bus-bar," refers, strictly 
speaking, only to those conductors on a switchboard 
which are connected directly to all of the machines. 
In common practice, however, it is understood that 
all of the current-carrying bars on a switchboard 
come under this classification. For high voltages it 
is usual to cover the bars with insulation, but for low 
voltages it is customary to leave them bare. The 
proper separation of bus-bars is 2-J inches for volt- 
ages less than 300, and 4 inches for the higher, in- 
cluding 550 volts. Copper and aluminum are used. 
Systematize bus-bars by placing all positive poles at 
top or right-hand- side of circuit. A current density 
of 1000 amperes per square inch is common practice 
for bus-bars, but is too high for the large ones. 

Table number VII shows the current-carrying 
capacity of bus-bars calculated on a basis of -1000 
amperes per square inch cross section. For very 
small bars 1-J times as much current may be allowed, 
while for the very large ones not more than half the 
current given in the table should be used. The carry- 
ing capacity of aluminum is given as 84 per cent of 
that of copper. 

Bushings. — In connection with very high voltages, 
specially constructed bushings must be used through 
walls. Ordinary bushings cause trouble. If possible 
the wires should be run in without touching any- 
thing. 



. 



ELECTRICAL TABLES AND DATA 









TABLE VII 










Table of Bus-Bar Data 


Carrying Capacity 












1000 


Amperes 












Amp. Per Sq. In. 


-tick 




Area in 


Lbs. 


Per Foot 


Per Sq. In 


. Alumi- 


ness 


' Width 


Sq. in. 


Copper 


Aluminum 


Copper 


num 


A 


i 


.0313 


.1205 


.0361 


32 


27 


-h 


i 


.0469 


.1807 


.0542 


47 


39 


& 


i 


.0625 


.2410 


.0723 


63 


53 


& 


« 


.0938 


.3615 


.1084 


95 


80 


i 


i 


.0625 


.2410 


.0723 


63 


53 


ft 


i 


.0938 


.3615 


1084 


95 


80 


§ 


i 


.1250 


.4820 


.1446 


125 


105 


* 


li 


.1875 


.7230 


.2169 


188 


158 


§ 


2 


.2500 


.9640 


.2892 


250 


210 


i 


1 


.1875 


.7230 


.2169 


188 


158 


I 


1 


.2500 


.9640 


.2892 


250 


210 


1 


U 


.3125 


1.205 


.3615 


315 


265 


1 


14 


.3750 


1.446 


.4338 


375 


315 


£ 


If 


.4375 


1.687 • 


.5061 


435 


365 


i 


2 


.5000 


1.928 


.5784 


500 


420 


i 


21 


.5625 


2.169 


.6507 


565 


475 


i 


2i 


.6250 


2.410 


.7230 


625 


530 


i 


I 


.3750 


1.446 


.4338 


375 


310 


1 


1 


.5000 


1.928 


.5784 


5C0 


420 


1 


U 


.6250 


2.410 


.7230 


625 


525 


I 


n 


.7500 


2.892 


.8676 


750 


630 


1 


if 


.8750 


3.374 


1.1122 


875 


735 


i 


2 


1.000 


3.856 


1.1568 


1000 


840 


| 


2-i 


1.125 


4.338 


1.3014 


1125 


995 


2 


21 


1.250 


4.820 


1.4460 


1250 


1050 


1 


2f 


1.375 


5.304 


1.5912 


1375 


1155 


I 


3 


1.500 


5.784 


1.7352 


1500 


1260 


1 


3i 


1.625 


6.266 


1.8798 


1625 


1365 


1 


31 


1.750 


6.748 


2.0244 


1750 


1470 


i 


3f 


1.875 


7.230 


2.1690 


1875 


1575 


i 


4 


2.000 


7.712 


2.3136 


2000 


1680 


1 


1 


.750 


2.892 


.8676 


750 


63Q 


1 


li 


1.125 


4.338 


1.3014 


1125 


945 


t 


2 


1.500 


5.784 


1.7352 


1500 


1260 


1 


21 


1.875 


7.230 


2.1690 


1875 


1575 


t 


3 


2.250 


8.676 


2.6118 


2250 


1890 


1 


31 


2.625 


10.122 


3.0366 


2625 


2260 


1 


4 


3.000 


11.568 


3.4704 


3000 


2520 



28 ELECTRICAL TABLES AND DATA 

The Aluminum Company of America recommends 
1200 amperes per square inch for the smaller bars 
and 500 for the largest. 

Cabinets. — Metal cabinets only are used in con- 
nection with conduit systems. Cabinets are obtain- 
able in four thicknesses of steel, viz., 16, 14, 12, and 
10 U. S. Standard gauge, equal to 1/16, 5/64, 7/64, 
and 9/64 inches respectively. The thin metal is used 
only for the smaller boxes, and the heavy for the 
large ones. The depth of cabinets is usually great 
enough to allow door to close with small switches 
in any position, and the large ones thrown way 
back. For necessary dimensions, see Cut-outs, Panel 
Boards, or Switches. "Where conduits enter all from 
one end, a wiring gutter space equivalent to about 
i square inch for each circuit of number 14 twin 
conductor should be allowed. Cabinets should be 
provided to enclose all cut-outs. If practicable, 
locate them so as to reduce likelihood of rubbish 
being stored in them to a minimum. To locate 
switches outside of cut-out cabinets is good practice. 
In ordering cabinets note the following points; Wood 
or metal. Wall or flush mounting. With or without 
lining. With or without wiring gutter. Thickness 
of steel desired. Over-all dimensions of cut-outs, 
panel board, or switch. Inches of back wiring 
pocket. Inches of side wiring pocket. Spring hinges 
or not. Type of handle or lock. Side on which 
hinge must be. Finish and nature of door. 

Candle Power. — This term is rather loosely used 
and has no very definite meaning, unless qualified 
by one of the following terms: Apparent candle 
power ; equivalent candle power ; mean lower hemi- 
spherical candle power; mean horizontal candle 
power; maximum candle power. The candle power 
of no lamp is the same in all directions. 



ELECTRICAL TABLES AND DATA 29 

Canopies. — The number of lamps to be used for 
the illumination of outlines in canopies is usually 
governed by the design of the canopy. The best 
effect, where outline lighting is to be installed, is 
obtained from many small lamps of low intrinsic 
brilliancy. Keep lamps and sockets out of the 
weather. Fixture canopies must be insulated wher- 
ever an insulating joint is called for on fixture. 

Carbons. — For life of carbons with various types 
of arc lamps, see Arc Lamps. The upper carbon is 
usually the positive, and for projecting arcs is larger 
than the lower. The positive carbon holds its heat 
longer than the negative. If carbons are too large, 
the arc will travel around them. With direct cur- 
rent, the upper or positive carbon is consumed twice 
as fast as the other. Flaming arc carbons contain 
special materials in the core, and the color of the 
arc is governed by this material. 

Car Houses. — A main switch is usually provided 
by which all wires in the car house can be cut off. 
Where a car house contains many sections it is better 
to provide a switch for each section. The illumina- 
tion of car houses is usually by series incandescent 
lighting. 

Carriage Calls. — These are usually made up in the 
form of electric signs, and located above canopies 
of theatres and hotels. They consist of a large num- 
ber of monograms and require a large number of 
wires to be run to them. Outdoor wires should be 
run in water-tight conduit system. If armored cable 
is used outdoors it must be lead-covered insulation. 

Cathode. — The cathode is the negative pole. This 
term is used in connection with batteries and electro- 
lytic devices, mostly. 

Ceiling Fans. — These must never be fastened 
rigidly, but in such a manner as to allow them to 
find their own "centers" when running. Not more 



30 ELECTRICAL TABLES AND DATA 

than 660 watts may be connected to one circuit. 
One fan to 400 or 500 square feet floor space is com- 
mon practice. 

Celluloid is highly inflammable, and must never 
be used exposed to heat or flame. "Where a trans- 
parent medium of a similar appearance is needed, 
gelatine is used. 

Cement when wet is a good conductor and may 
easily cause grounds. 

Centers of Distribution. — In most cases the loca- 
tion of centers is governed by other conditions than 
economy of copper, and is dictated by the desire of 
the user. Where, however, free choice of location 
is given, the following tabulation showing the rela- 
tive number of circular mils for each branch cir- 
cuit of 660 watts at 110 volts will be of use. The 
table shows that with small mains, and especially 
three-wire systems, the amount of copper in the 
mains may be much less than in the branch circuits, 
and that it will be more profitable to run mains into 
the area to be served. This advantage grows less 
with larger mains. Branch circuits require 8214 
circular mils per circuit of 660 watts. 

The theoretical requirements per 660 watts for 
mains supplying centers is given below: 





TABLE Vin 




Mains B. & S. 


2 Wire 


3 Wire 


14 


3286 


2460 


12 


3957 


2968 


10 


5000 


3752 


8 


5693 


4270 


6 


6325 


4744 


5 


7227 


5426 


4 


7200 


5397 


3 


7914 


5934 



Chandeliers. — No part of any chandelier should 
less than six feet two inches above floor. The usual 



. 



ELECTRICAL TABLES AND DATA 31 

height ranges between this and seven feet. In thea- 
tres and similar places where chandeliers hang very 
high, arrangement should be made for. either raising 
or lowering to admit of lamp renewals. For large 
chandeliers special permission to rise 1320-watt cir- 
cuits can usually be obtained. 

Chemical Works. — Before undertaking work in 
such places, investigate the nature of fumes, and 
chemicals used, with reference to effect upon copper 
and insulating materials, especially metal conduits,, 
if considered. 

Choke Coils. — These are used mostly in connec- 
tion with lightning arresters. They must be as well 
insulated- as the circuit wires to which they are- 
connected. 

Churches. — Some of the large churches require a 
lighting equipment similar to that of theatres. In 
choir lofts and at altars, pockets for special lights 
are often required. Indirect lighting is very useful 
in churches, as the light should be kept out of the 
line of vision of the speaker as well as the audience. 
From two to three foot candles are necessary. Emer- 
gency lighting should also be provided. 

Circuit Breakers are much more sensitive than 
fuses. Many of them are so constructed as to allow 
a considerable overload for a short time, and the 
length of this time is adjustable. Circuit breakers 
should ordinarily not be set more than 30 per cent 
above the rated carrying capacity of the wire they 
are to protect. 

Coils. — The coils of a magnet must be connected 
so as to form a continuous spiral. 

Coloring Lamps. — Coloring and frosting of lamps 
reduces the light from 30 to 50 per cent. Amber 
coloring reduces the light about 20 per cent, while 
green and red take up from 50 to 90 per cent, 
according to the density and shade. Prepared color- 



i 



32 ELECTRICAL TABLES AND DATA 

ing materials can be had at all supply stores. A few 
amber-colored lamps are sometimes mixed in with 
white lights to give a warmer glow to the light. 

Color of Light Sources. — 

Moore tube (carbon dioxide gas) White 

Intensified arc White 

Magnetite arc White 

Open arc Nearly white 

Tungsten lamp Nearly white 

Tungsten lamp, gas-filled White 

Nernst lamp Nearly white 

Enclosed arc (short arc) Bluish white 

Tantalum lamp Pale yellowish white 

Gem lamp Pale yellowish white 

Carbon lamp Pale yellowish white 

Regenerative flame arc Yellow 

Flaming arc Variable with different carbons 

Mercury lamp (glass tube) Bluish green 

Enclosed arc (long arc) Bluish white to violet 

High sun White 

Low sun Orange red 

Skylight Bluish white 

Welsbach mantle Greenish white 

Common gas burner Pale orange yellow 

Kerosene lamp Pale orange yellow 

Candle Orange yellow 

TABLE IX 

Comparison of Fahrenheit and Centigrade Thermometers 

Pah. Cent. Fah. Cent. Fah. Cent. Fah. Cent. Fah. Cent. 



212 


100 


165 


73.8 


118 


47.7 


71 


21.6 


24 


— 4.4 


211 


99.4 


164 


73.3 


117 


47.2 


70 


21.1 


23 


— 5.0 


210 


98.8 


163 


72.7 


116 


46.6 


69 


20.5 


22 


— 5.5 


209 


98.3 


162 


72.2 


115 


46.1 


68 


20.0 


21 


— 6.1 


208 


97.7 


161 


71.6 


114 


45.5 


67 


19.4 


20 


— 6.6 


207 


97.2 


160 


71.1 


113 


45.0 


66 


18.8 


19 


— 7.2 



ELECTRICAL TABLES AND DATA 33 

Fall. Cent. Fah. Cent. Fah. Cent. Fah. Cent. Fah. Cent. 

206 96.6 159 70.5 112 44.4 65 18.3 18 — 7.7 

205 96.1 158 70.0 111 43.8 64 17.7 17 — 8.3 

204 95.5 157 69.4 110 43.3 63 17.2 16 — 8.8 

203 95.0 156 68.S 109 42.7 62 16.6 15 — 9.5 

202 94.4 155 68.3 108 42.2 61 16.1 14 —10.0 

201 93.8 154 67.7 107 41.6 60 15.5 13 —10.5 

200 93.3 153 67.2 106 41.1 59 15,0 12 —11.1 

199 92.7 152 66.6 105 40.5 58 14.4 11 —11.6 

198 92.2 151 66.1 104 40.0 57 13.8 10 —12.2 

197. 91.6 150 65.5 103 39.4 56 13.3 9 —12.7 

196 91.1 149 65.0 102 38.8 55 12.7 8 —13.3 

195 90.5 148 64.4 101 38.3 54 12.2 7 —13.8 

194 90.0 147 63.8 100 37.7 53 11.6 6 —14.4 

193 89.4 146 63.3 99 37.2 52 11.1 5 —15.0 

192 88.8 145 62.7 98 36.6 51 10.5 4 —15.5 

191 88.3 144 62.2 97 36.1 50 10.0 3 —16.1 

190 87.7 143 61.6 96 35.5 49 9.4 2 —16.6 

.189 87.2 142 61.1 95 35.0 48 8.8 1 —17.2 

188 86.6 141 60.5 94 34.4 47 8.3 —17.7 

187 86.1 140 60.0 93 33.8 46 7.7— 1 —18.3 

186 85.5 139 59.4 92 33.3 45 7.2— 2 —18.8 

185 85.0 138 58.8 91 32.7 44 6.6 — 3 —19.4 

184 84.4 137 58.3 90 32.2 43 6.1—4 —20.0 

183 83.8 136 57.7 89 31.6 42 5.5— 5 —20.5 

182 83.3 135 57.2 88 31.1 41 5.0— 6 —21.1 

181 82.7 134 56.6 87 30.5 40 4.4— 7 —21.6 

180 82.2 133 56.1 86 30.0 39 3.8— 8 —22.2 

179 81.6 132 55.5 85 29.4 38 3.3— 9 —22.7 

178 81.1 131 55.0 84 28.8 37 2.7—10 —23.3 

177 80.5 130 54.4 S3 28.3 36 2.2—11 —23.8 

176 80.0- 129 53.8 82 27.7 35 1.6—12 —24.4 

175 79.4 128 53.3 81 27.2 34 1.1—13 —25.0 

174 78.8 127 52.7 80 26.6 33 0.5—14 —25.5 

173 78.3 126 52.2 79 26.1 32 .0—15 —26.1 

172 77.7 125 51.6 78 25.5 31 —0.5—16 —26.6 

171 77.2 124 51.1 77 25.0 30 —1.1—17 —27.2 

'70 76.6 123 50.5 76 24.4 29 —1.6—18 —27.7 

169 76.1 122 50.0 75 23.8 28 —2.2—19 —28.3 

168 75.5 121 49.4 74 23.3 27 —2.7—20 —28.8 

167 75.0 120 48.8 73 22.7 26 —3.3 

166 74.4 119 48.3 72 22.2 25 —3.8 

To convert degrees Centigrade into Fahrenheit, if 

the temperature given is above zero, multiply by 1.8 



34 ELECTRICAL TABLES AND DATA 

and add 32. If it is below zero multiply also by 1.8, 
but if this product is less than 32, subtract it from 
32 ; if more, subtract 32 from it. To convert Fahren- 
heit into Centigrade, if the temperature given is above 
zero, subtract 32 and divide the remainder by 1.8 ; if 
below zero, add 32 and divide by 1.8. 

Concentric Wire. — Concentric wires are seldom 
used except in mines and similar places. Such a 
wire fully insulated would require more insulating 
material and be more bulky than the ordinary duplex 
wire. The concentric wire recently put upon the 
market has only one wire insulated. The other wire 
is a metal sheath which entirely surrounds the inner 
wire and its insulation. The sheath must always be 
thoroughly grounded. 

Condensers must be enclosed in noncombustible 
cases and installed with the same precautions as the 
wires of the system to which they attach. Con- 
densers are usually rated in microfarads, and a 
condenser of two or three microfarads is considered 
quite large. 

Conduits. — Conduit installations materially reduce 
the fire hazard, but to some extent increase the 
minor troubles. They produce many grounds and 
short circuits, but confine the trouble. Careful work- 
manship, especially at junction and outlet boxes, 
will reduce such troubles to a minimum. Install 
conduits so they will drain, and avoid their use in 
wet places unless lead-encased wires are used. . 
Skilled conduit workers avoid the use of elbows with 
small wires as much as possible. The following 
tables (X and XI) give the sizes of conduits recom- 
mended by the National Electrical Contractors' 
Association of the United States in connection with 
various sizes and numbers of wires. These recom- 
mendations are based on actual tests and can be 
relied upon. 



ELECTRICAL TABLES AND DATA 35 

TABLE X 

Standard sizes of conduits for the installation of wires and 
cables as adopted and recommended by The National Elec- 
trical Contractors' Association of the United States and the 
N. E. Code. 

Conduit sizes are based on the use of not more than three 
90° elbows in runs taking up to and including No. 10 wires; 
and two elbows for wires larger than No. 10. Wires No. 8, 
and larger, are stranded. 

One "Wire Two Wires Three Wires Four Wires 
Approx. in a Conduit in a Conduit in a Conduit in a Conduit 
B. & S. Diameter , — Diam. . , — Diam. — , , — Diam.— N , — Diam.' — ^ 



Gauge 


of Wii 


e Int 


Ext.' Int. 


Ext 


. Int. 


Ext 


Int. 


Ext. 


14 


18 / 6 4 


% 


.84 


y 2 


.84 


% 


.84 


% 


1.05 


12 


2 %4 


y 2 


.84 


% 


1.05 


% 


1.05 


% 


1.05 


10 


2 %4 


% 


.84 


% 


1.05 


% 


1.05 


1 


1.31 


8 


2 %4 


% 


.84 


i 


1.31 


1 


1.31 


1 


1.31 


6 


3 %4 


% 


.84 


i 


1.31 


iy 4 


1.66 


1% 


1.66 


5 


31 /64 


% 


1.05 


i% 


1.66 


1% 


1.66 


1% 


1.66 


4 


3 %4 


% 


1.05 


i% 


1.66 


1% 


1.66 


1% 


1.90 


3 


3 %4 


% 


1.05 


i% 


1.66 


1% 


1.66 


1% 


1.90 


2 


3 %4 


% 


1.05 


i% 


1.66 


iy 2 


1.90 


1% 


1.90 


1 


4 %4 


% 


1.05 


i% 


1.90 


1% 


1.90 


2 


2.37 





4 %4 


i 


1.31 


i% 


1.90 


2 


2.37 


2 


2.37 


00 


4 %4 


i 


1.31 


2 


2.37 


2 


2.37 


2y 2 


2.87 


000 


5 %i 


i 


1.31 


2 


2.37 


2 


2.37 


2y 2 


2.87 


0000 


5 %4 


U4 


1.66 


2 


2.37 


2y 2 


2.87 


2% 


2.87 


250,000 


5 %4 


1% 


1.66 


2% 


2.87 


2y 2 


2.87 


3 


3.50 


300,000 


6 %4 


1V4 


-1.66 


2% 


2.87 


2% 


2.87 


3 


3.50 


400,000 


6 %4 


1% 


1.66 


3 


3.50 


3 


3.50 


3% 


4.00 


500,000 


7 %4 


1% 


1.90 


3 


3.50 


3 


3.50 


3% 


4.00 


600,000 


8 %4 


l% 


1.90 


3 


3.50 


3% 


4.00 






700,000 


8 %4 


2 


2.37 


3% 


4.00 


3% 


4.00 






800,000 


8 %4 


2 


2.37 


3% 


4.00 


4 


4.50 






900,000 


9 %4 


2 


2.37 


3y 2 


4.00 


4 


4.50 






1,000,000 


97 / 6 4 


2 


2.37 


4 


4.50 


4 


5.00 






1,250,000 


10 %4 


2% 


2.87 


4y 2 


5.00 


4y 2 


5.00 






1,500,000 


117 /64 


2y 2 


2.87 


4% 


5.00 


5 


5.56 






1,750,000 


12 %4 


3 


3.50 


5 


5.56 


5 


5.56 






2,000,000 


133/ 64 


3 


3.50 


5 


5.56 


6 


6.62 












Duplex Wires 










14 


3 %4 


y 2 


.84 


% 


1.05 


1 


1.31 


1 


1.31 


12 


3 %4 


y 2 


.84 


% 


1.05 


1 


1.31 


l 1 /! 


1.66 


10 


3 %4 


% 


1.05 


1 


1.31 


1% 


1.66 


1%. 


1.66 



36 ELECTRICAL TABLES AND DATA 

TABLE XI 

Standard sizes of conduits for the installation of wires and 
cables. 

3 "Wire Convertible System 3 Wire Convertible System 



2 Wires 




Size 


2 Wires 




Size 


B.&S. 


1 Wire 


Conduit 


B. & S. 


1 Wire 


Conduit 


14 


10 


% 


00 


350,000 


2y 2 


12 


8 


% 


000 


400,000 


2y 2 


10 


6 


1 


0000 


550,000 


3 


8 


4 


1 


250,000 


600,000 


3 


6 


2 


1% 


300,000 


800,000 


3 


5 


1 


1% 


400,000 


1,000,000 


3y 2 


4 





1% 


500,000 


125,000 


4 


. 3 


00 


1% 


600,000 


1,500,000 


4 


2 


000 


iy 2 


700,000 


1,750,000 


4y 2 


1 


0000 


2 


800,000 


2,000,000 


4y 2 





250,000 


2 









Single Wire Combination. 

Number of single No. 14 wires in one conduit. Straight run; 
no elbows. Special permission is required. 

Conduit Size 

3 No. 14 rubber covered double braid % 

5 No. 14 rubber covered double braid % 

10 No. 14 rubber covered double braid 1 

18 No. 14 rubber covered double braid 1% 

24 No. 14 rubber covered double braid 1% 

40 No. 14 rubber covered double braid. 2 

74 No.. 14 rubber covered double braid 2y 2 

90 No. 14 rubber covered double braid 3 



Signal Systems. 
Straight runs; no elbows. 



No. Wires B.& S. 



Conduit Sizes 



10 16 Lt. ins. fixture wire V2 

20 16 Lt. ins. fixture wire % 

30 16 Lt. ins. fixture wire 1 

70 16 Lt. ins. fixture wire 1% 

90 16 Lt. ins. fixture wire 1% 



ELECTRICAL TABLES AND DATA 



No. Wires 


B.&S 








150 


16 


Lt. 


ins. 


fixture wire 


18 


18 


Lt. 


ins. 


fixture wire 


30 


18 


Lt. 


ins. 


fixture wire 


40 


18 


Lt. 


ins. 


fixture wire 


100 


18 


Lt. 


ins. 


fixtrue wire 


130 


18 


Lt. 


ins. 


fixture wire 


200 


18 


Lt. 


ms. 


fixture wire 



Conduit Sizes 
2 



i 

i% 

i% 

2 

Telephone Circuits. Not more than two 90° Elbows. 

No. 19 braided and twisted No. 20 braided and twisted 

pair switchboard or desk pair switchboard or desk 

instrument wires. instrument wires. 

No. Pairs Conduit No. Pairs. Conduit 

3 % 5 y 2 

6 % 10 % 

10 1 15 1 

16 li/i 25 1% 

25 1% 35 iy 2 

35 2 50 2 

Conduits and Wires. — Two sides of the smallest 
rectangular enclosures that will contain a given 

D 
number of wires are : (Dxa) + — and D x h x 86. D 

2 
being the diameter of the wire, a the number of wires 
in longest row, and b the number of rows. 

The nearer square this enclosure can be made, the 
greater the economy of material. The greatest number 
of wires that can be placed in a rectangular enclosure 



\D 'y X \Dx.86J 



L being the length of the enclosure, E the height, 
and D the diameter of the wire. 

This formula is only approximate and in using it 

all fractions obtained by -^ and ^ — ^r must be 

_ D Dx.86 

dropped. 



38 ELECTRICAL TABLES AND DATA 

Example. — Given an enclosure 6 inches long and 2 
inches high, how many wires can it hold, the diam- 
eter of each wire being .7? 6 divided by .7 equals 
8.6. Dropping the .6 and subtracting \, we have 7.5 
for the first factor. Next, .7 times .86 equals .602; 
2 divided by this equals 3.3 ; dropping the .3, we 
now have to multiply the 7.5 by 3, which equals 22.5, 
or 22 wires. 

For circular enclosures no general formula can 
be given because the percentage of waste space 
varies greatly with different wires. The first chart 
may be used to determine the smallest conduit that 
will enclose a certain number of wires. This chart 
shows graphically how nearly different numbers of 
wires fill out circular spaces. To use this chart, 
multiply diameter of wire by the number given in 
connection with circle containing the requisite num- 
ber of wires. This will give the smallest diameter 
of tube or conduit that will receive these wires. 
How much larger the conduit to be used must be 
depends upon circumstances. The number and na- 
ture of bends, nature of insulation, flexibility of 
wire, as well as temperature and inspection require- 
ments, must be taken into consideration. 

The charts illustrate the relative spaces occupied 
by the different conduits, viz. : 3", 2£", 2'', \\" , \\" , 
1", etc., and the wires considered. The sizes of con- 
duits are marked in the various circles and each 
horizontal row pertains to one size of wire, with 
exception of the 4th and 5th in each row and a few 
at the top of one of the charts. The 4th shows a 
neutral wire of half the carrying capacity, and the 
5th of double the carrying capacity of the outside 
wires. The different sizes of conduit given in each 
case will enable one to judge the most appropriate 
size to be used under different circumstances. The 
wires shown are all double braid stranded cables. 



ELECTRICAL TABLES AND DATA 




ELECTRICAL TABLES AND DATA 



1000000 
CM. 




1250000 

CM. 




1500000 

CM. 




800000 CM. 




(D 



900000 CM. 




(D 



600000 C 





700000 C 





500000 CM- 




400000 CM. 




300000 CM. 




250000 CM. 



ELECTRICAL TABLES AND DATA 




OOOB.&S. 







OOB.&S 




OB.&S 




1B.&S. 








2B.&S. 






3B.&S. 



i 






42 ELECTRICAL TABLES AND DATA 

In the preceding pages are given the conduit sizes 
recommended by the National Electrical Contractors' 
Association of the United States. These should be 
followed as far as they apply. 

Contacts. — The standard materials for mounting 
contacts are slate, marble, porcelain, and glass. 
Where these are liable to breakage, other materials 
are allowed, but they should always be submitted 
to inspection departments for approval. A surface 
contact of one square inch for each 75 amperes is 
good practice for knife-switches and similar devices. 

Controllers. — Methods of motor and light control 
are numerous. Lights are usually controlled by 
cutting resistance into the mains. A certain con- 
troller is suitable only for a certain number of lights 
requiring a certain amperage. The reduction of 
voltage is equal to the product of the amperes times 
the resistance, and the effect upon the lights is 
greater than indicated by the drop in voltage. The 
speed of motors may be altered by cutting resist- 
ance into the mains, altering the field connections, 
arranging taps of different voltages, and connecting 
armatures in multiple or series. 

Cooking. — Almost any kind of cooking can be 
accomplished electrically, but the expense is higher 
than with gas. It is best to be honest and advise 
customers correctly about these things than to 
cause disappointment. The advantages are con- 
venience and rapidity of results with many of the 
devices. 

Cooper-Hewitt Lamps (Mercury Vapor). — These 
lamps may be obtained for either alternating or 
direct-current use, and for 110 or 220 volts. The 
light given out is of a greenish hue, and gives a 
ghastly effect to faces and hands. Many persons 
object to working under it, while others seem to 
like it. The efficiency of the lamp compares favor- 



ELECTRICAL TABLES AND DATA 43 

ably with others ; it is easy to operate, and the light 
is practically shadowless. With alternating currents 
the light flickers somewhat, and is said to give a 
deceptive appearance to some surfaces. Not more 
than one lamp should be installed on one circuit. 
Use double-pole switches and avoid plug cut-outs for 
220 volts. Current sent through direct-current lamps 
in wrong direction will ruin tubes. Where inflam- 
mable gases exist, the sparking of some of the lamps 
is dangerous. The life of a tube is now claimed to 
be 5000 hours. The current ranges from 3.5 to 2.0 
amperes for different types, and the efficiency is 
given as from 0.51 to 0.64 watts per mean lower 
hemispherical candle power. The light is mostly 
thrown downward. 

Copper weighs about 556 pounds per cubic foot; 
its specific gravity is about 8.9, and it melts at 1196 
degrees Fahrenheit. The tensile strength of an- 
nealed copper may be taken as about 35,000 pounds 
per square inch, and that of hard drawn copper as 
about 55,000. 

Cross Currents pass between A.C. generators, and 
also between synchronous motors when they are 
operating in parallel and not perfectly in phase. 
These currents heat the wires and overload the 
machines unnecessarily. 

Cut-outs. — In connection with installations served 
by central stations, the type of cut-out and fuse 
preferred by that company should be installed. This 
will usually obtain free fuse renewals. The installa- 
tion of cartridge-type fuses is not advisable except 
in establishments where a competent electrician is 
always on duty. 

The dimensions of several types of cut-outs are 
given below. 



ELECTRICAL TABLES AND DATA 

TABLE XII 

Paiste Panel Cut-Outs (See Figure 2). 

125 Volt Sizes. Capacity of Switches 30 Amperes 




Figure 2. — Paiste Panel Cutouts. 



Cat. No. 


Main 


Branches 


Width 
(inches) 


Length 
(inches) 


4012 
4015 
4026 
4013 

4103 


2-Wire 
2-Wire 
3-Wire 
3-Wire 
3-Wire 


Single, 2-Wire 
Double, 2-Wire 
Single, 2-Wire 
Double, 2-Wire 
Single, 3-Wire 


3% 

3 

3% 
3% 
5 


5% 
10% 

7% 
10% 

8% 


250 


Volt Sizes 


. Capacity of Switches 30 


Amperes 


=4101 
=4105 


2-Wire 
2-Wire 


Single, 2-Wire 
Double, 2-Wire 


3% 

3% 


7 
11% 



ELECTRICAL TABLES AND DATA 

TABLE XIII 
Dimensions for Plug Cut-Outs (See Figure 3). 




No.2,165 



N0.8OU 

Figure 3. — Plug Cutouts. 



No. ^3 5 



it. No. 


Length 


Width 


Height 




(inches) 


(inches) 


(inches) 


2569 


2% 


2 


1« 


2965 


2V 2 


3^ 


111 


2165 


2 T % 


4y 2 


111 


8020 


3% 


3% 


1% 


1935 


m 


3^ 


HI 


2587 


6* 


3 


Hi 


2150 


4% 


3 


HI 


2109 


6* 


. 2i§ 


Hi 


t -, • -> 


m 


4|| 


HI 


Z1Z5 


6% 


4A 


Hi 



ELECTRICAL TABLES AND DATA 







7 &- 




-m 



3H 



rig 10 OP 0.8 



r. —a 



Fig II 3t»2wir» O.B 



-1 



14 



Fig 6 TP08 Rgia 2WiP* 

Figure 4.— D. & W. Cutouts. 



ELECTRICAL TABLES AND DATA 47 

TABLE XIV 

Dimensions of D. & W. 250 Volt Cut-Out's (See Figure 4). 

Amperes Fig. A B . C D E 



0-30 


1 


31 


1 


ift 


31 


li 


0-30 


2 


3ft 


2| 


ift 


3ft 


14 


0-30 


3 


3ft 


4 


ift 


3ft 


14 


0-30 


4 


41 


2| 


ift 


41 


14 


0-30 


5 


6 


4 


ift 


6 


14 


0-30 


10 


7| 


2| 


ift 


7| 


14 


0-30 


6 


. 8if 


4ft 


ift 


841 


14 


0-30 


11 


8*1 


21 


ift 


841 


14 


0-30 


12 


3* 


3| 


ift 


3s 


14 


31-60 


1 


41 


If 


iii 


5ft 


2| 


31-60 


2 


4-1 


3ft 


IS 


5ft 


1ft 


31-60 


3 


4| 


5" 


11 


5ft 


1ft 


31-60 


4 


61 


W 


11 


641 


1ft 


31-60 


5 


8 


5 


If 


8ft 


1ft 


31-60 


10 


10tt 


3| 


24 


us 


141 


31-60 


6 


12 


5ft 


24 


121 


Hi 


31-60 


11 


12 


314 


24 


121 


Hi 


61-100 


7 


64 


24 


2ft 


6S 


41 


61-100 


8 


81 


4ft 


2ft 


81 


141 


61-100 


9 


81 


61 


2ft 


81 


141 


101-200 


7 


71 


2| 


31 


84 


51 


201-400 


7 


9i 


31 


4ft 


104 


6f 


401-600 


7 


11 


3* 


4f 


12f 


81 



Delta Connection. — This method of connection is 
used only with three-phase a. c. currents. If the 
connection of a generator is changed from "star" 
to "delta," its current will be increased 1.73 times 



48 ELECTRICAL, TABLES AND DATA 

for the same power delivery. If it is changed from 
" delta' 3 to "star," its e.m.f. will be increased 1.73 
times. A synonymous term for delta is "mesh." 

Demand Factor. — At present it is customary among 
inspection bureaus to demand conductor capacity 
equivalent to the whole connected load operating at 
its maximum capacity. Experience, however, has 
shown that in many cases this leads to a great waste 
of copper. 

In very many installations it has been found that 
not over 20 per cent of the connected load is ever in 

















s 






















"H 


5* 










«5 






r 












5 


•^ 


^ 


** 


^» 










-is* 
























■*! 


ss? 


-51 


c*|«»c*M 



Demand Factor Chart. 



use at the same time. Tables of demand factors ap- 
plicable to many classes of service have been worked 
out and are in existence. But as far as the authors are 
aware, these are all arranged from the standpoint of 
the central station engineer and are hardly applicable 
to individual installations. As a matter of fact, the 
authors have failed to find any two installations, even 
in the same line of business, quite alike. 



ELECTRICAL TABLES AND DATA 49 

INDIVIDUAL MOTORS 

Many motors are now designed and rated to carry 
a certain overload, usually 25 per cent, for a short 
time. This fact should be taken into account wher- 
ever it seems necessary. Whenever motors are de- 
signed for a short time rating, instead of for con- 
tinuous use, it seems but right that the conductors be 
chosen with the same length of time in view. Insofar 
as the heating of conductors is concerned, it is un- 
necessary to pay any attention to the ordinary start- 
ing current. The only justification for the ex- 
cessive carrying capacity usually demanded for in- 
dividual motors, lies in a possible necessity to take 
care of overloads. 

GROUPS OF REGULARLY REVERSING MOTORS 

A graphic representation of current values in a 
series of cycles of operation of a reversible motor 
operating a large washing machine is given in Figure 
4b. In connection with such motors, it is quite usual 
to reverse without giving the armature time to come to 
rest. The reversed current through the armature 
must first bring the machinery to rest and then start 
it in the opposite direction. The majority of such 
motors reverse at intervals of 10 or 12 seconds and 
the average peak current lasts about one second. 

In this connection it will be well to note that, in 
order to give this study a practical value, we must 
take a course about midway between absolute accu- 
racy and haphazard guess work. The heating effect 
of various kinds of motor loads cannot be accurately 
determined without the use of graphic current charts 



SO 



ELECTRICAL TABLES AND DATA 



and these are seldom available at the time the installa- 
tion is made. The contractor and the inspector are 
thus, in the majority of cases, compelled to judge by 
the rated h. p. of the motors required. In order, 
therefore, to make these tables of general use to the 
public, the carrying capacity of conductors required 




Fig-ure 4'b 

must be based upon the h. p. intended to be installed. 
It is principally for this reason that the following 
table has been arranged in the form given. 

The table gives factors which express the ratio of 
the h. p. equivalent of intermittent or fluctuating 
currents to the heating equivalent of the same cur- 
rents. The h. p. value of a fluctuating current (volt- 
age assumed constant) is proportional to the average 
sum of all the ordinates of a curve representing it. 
The heating effect of the same current is proportional 
to the r. m. s. value of the same ordinates. Thus, if 
we divide the r. m. s. value of a certain fluctuating 
current by its h. p. value, we shall obtain a factor by 
which we may multiply the h. p. delivered by a motor 
in such service in order to find the amperage for which 
conductor capacity should be provided to guard 
against overheating. 



ELECTRICAL TABLES AND DATA 50a 

At the top of the table we have the various per- 
centages of time of minimum and peak currents. In 
the first vertical row we have various percentages of 
peak currents expressed in terms of the minimum 
current used. In this form we may use the factors in 
connection with the rated h. p. of the motors, pro- 
vided we know, in a general way, the approximate 
ratio of the minimum to the peak currents required 
by the fluctuating load. 

As an example: If we have a motor reversing 
regularly and requiring a peak current five times as 
.great as its running current, and this during half of 
the time of each cycle, we look where the lines per- 
taining to 50 per cent peak and minimum current 
time cross the line pertaining to the 500 per cent 
peak, and find there the factor 1.21, which indicates 
that the amperage to be provided for must be 1.21 
times that called for by the h. p. rating of the motor. 

Table 
Percent time 

of peak current. 10 20 30 40 50 60 70 80 90 
Percent time 

mm. current.. . . 90 80 70 60 50 40 30 20 10 

Percent f 200% 1.04 1.05 1.06 1.06 1.05 1.04 1.04 1.04 1.01 

peak load 300% 1.12 1.15 1.15 1.14 1.12 1.10 1.07 1.05 1.02 

in terms 400% 1.22 1.25 1.23 1.21 1.17 1.13 1.10 1.07 1.03 

of min. 500% 1.31 1.34 1.30 1.26 1.21 1.16 1.11 1.07 1.03 

!oad..<| 600% 1.41 1.42 1.37 1.29 1.23 1.18 1.12 1.08 1.04 

700% 1.50 1.50 1.40 1.32 1.25 1.19 1.13 1.09 1.04 

800% 1.59 1.54 1.44 1.35 1.27 1.20 1.15 1.09 1.04 

900% 1.67 1.59 1.47 1.37 1.28 1.21 1.15 1.09 1.04 

1 1000% 1.74 1.63 1.50 1.39 1.29 1.22 1.15 1.09 1.04 

The factors here given are correct for single motors 
and are based on the worst possible condition under 
which a group of motors can operate; viz., all peaks 
superimposed. This is a condition which may at times 



50b ELECTRICAL. TABLES AND DATA 

be attained, but if a large group of motors is con- 
sidered, the chance of its recurrence is exceedingly 
small. 

With these considerations in view, we deduce the 
following formula to find the fraction of the total 
time during which the peaks of all the motors in use 
are likely to be superimposed : 
A b 

In this formula, A represents the fraction of the 
time of a cycle of operation during which the peak 
is in use, and b the number of motors in use. In the 
case of laundry motors of the characteristics shown 
in Figure 4b, the peaks, when once coincident, will 
remain so for some length of time or until one or more 
have been stopped and the combination broken. In 
the case of elevator motors the combination will al- 
most immediately be broken. 

GROUPS OF REVERSING MOTORS WITH VARIABLE TIME 
INTERVALS 

In many machine shops the planers are equipped 
with reversing motors. Some very clever systems of 
dontrol have been worked out and in some of these 
the carriage is made to return at a high rate of speed 
after making the cut. The length of time during 
which such a motor moves in either direction is 
variable and the power required by the forward and 
return strokes is also variable. The periodicity, as 
well as the relative amount of current, vary and are 
governed by the work in hand. 

Since there is no permanent regularity about any 
of the operations, no exact forecast as to what will 
happen at any particular time can be made. A study 



ELECTRICAL TABLE'S AND DATA 



of the conditions as illustrated in Figure 4c will, 
however, assist materially in judging what the cur- 
rent demands of a group of such motors may be at 
times. 

In the figure we have five motors, denoted by black 
circles, in operation and reversing regularly at in- 
tervals of 12, 6, 8, 4 and 9 seconds. An inspection of 
the figure will show at a glance that, with any num- 



Figure 4=c 

ber of motors, if they start in synchronism, the time 
of coincidence of the peak of all of them will be pro- 
portional to the least common multiple of all of their 
time intervals. In this case that number is 72 ; hence, 
at intervals of 72 seconds these motors will all come 
into synchronism as far as their peaks are concerned. 
Their minima of current will, of course, also come into 
synchronism regularly. 

If they do not start in synchronism, those starting 
at time intervals which form a multiple of their own 
time, remote from that of other motors, will work into 
synchronism and out of it in a perfectly regular 
manner, just as will those shown in the figure. Those 
that start at different time intervals, however, will 
not. 

As an example, if the motor having a period of 6 
seconds starts either 1, 2, 3, 4, 5, 7, 8, 9, 10 or 11 
seconds after the other, it will never superimpose its 



50d ELECTRICAL TABLES AND DATA 

peak entirely upon that of the other, although a part 
of it may overlap. It must, however, be borne in mind 
that the motor having the shortest periods governs 
the chances of falling into step. A motor having a 
period of 4, for instance, will have only one chance 
in 4 of missing regular synchronism of peaks with 
other motors having periods of 8 or 12. With motors 
on this kind of work then, we may be certain that 
there will be coincidence of peaks at times. In con- 
nection with motors of this kind it will be safe to use 
about the average multipliers given in the table, the 
average being determined from the characteristics of 
the different motors. 

PASSENGER ELEVATOR AND SIMILAR MOTORS 

In the kind of service here considered, the current 
is either entirely on or off. If calculations are to be 
based upon current or power charts the equivalent 
current of a cycle of operations should be determined 
by the r. m. s. method. The formulae and the tables 
herewith furnished, however, are so arranged that, 
for general purposes, we need merely know the rated 
h. p. of the whole group and the relative time of the 
on and off periods. 

In the preliminary operation of finding the current 
required it is to be assumed that the motors are de- 
livering their rated capacity continuously, regardless 
of the nature of their rating. The formula given 
below is also independent of the number of motors 
and the demand factor obtained is a function of the 
relative on and off times of the motors, which is 
assumed to be the same for all. 

A conductor is used to the best advantage with 



ELECTRICAL TABLE'S AND DATA 50e 

reference to heating when subjected to a steady cur- 
rent flow. Hence, if another conductor be called upon 
to transmit an equivalent amount of energy with 
intermittent service, the carrying capacity of the ' 
second conductor must be correspondingly increased. 
If the load is of such a nature that the- conductor is 
idle half of the time, it must carry double current 
during the other half of the time. As the heating is 
proportional to the square of the current, it follows 
that a double current during half time is equivalent 
in heating effect to V2 times the normal current used 
continuously. The same relation holds for all other 
time divisions and this will allow us to find the value 
of a steady current, to be denoted by I, which will 
be the equivalent of any regularly intermittent cur- 
rent of the nature here considered by the formula as. 
, given below: 



\fJrXW 



where i is the theoretical current based on the total 
motor rating, t the fraction or percentage of time in 
a cycle of operation during which the motor is using 
this current, and V the time of a complete cycle of 
operation. This formula will give us a multiplier, 
virtually a demand factor, by which we can find the 
current having an equivalent heating effect to that 
required by the motors under the assumption that 
they are all working under the worst possible condi- 
tion, i. e., all motors taking their maximum current 
at the same instant. 

The factors calculated according to the formula 
as applying to the various percentages of time dur> 



50f ELECTRICAL TABLES AND DATA 

ing which the current is in use, are given below. The 
upper line gives the percentage of time during which 
current is used, and the lower line gives the multiply- 
ing factors. 

Percentage of Time 10 20 30 40 50 60 70 80 90 

Factors 32 .45 .55 .66 .71 .78 .84 .89 .95 

^GROUPS OF MOTORS OF INDISCRIMINATE CHARACTERISTICS 

This classification embraces all kinds of motors as 
usually found in shops .and factories. There are two 
ways of arriving at the probable demand factor of 
such groups. One way consists of consulting tables 
made up from experiences with similar installations. 
This method has the great disadvantage that it is 
almost impossible to find two installations near enough 
alike to warrant very accurate comparisons. Such 
tables are given further on, but should be used only 
as general guides and the final determination made 
only after making a careful analysis of the installa- 
tion. 

A simple method of analyzing a motor installation 
and determining its demand factor is as follows : Take 
any piece of ordinary ruled paper and number as 
many lines as there are hours of the day to be con- 
sidered. Let these lines be horizontal. Next draw as 
many lines vertically across them as there are motors 
to be considered. Also place each line so that in 
position and length it may cover the hours of the day 
during which the motors are thought to be in use. 

There are two ways in which such a representation 
can be made. If the motors have no fixed time at 
which they run, their running time may be laid out 
.-at the bottom of the figure ; the main point being that 






ELECTRICAL. TABLES AND DATA 51 

the lines give a fair idea of the proportionate running 
time per day. If the stopping and starting intervals 
are not too short, a series of snch lines, representing 
the estimated number of starts, may be used. 

If any of the motors are used only during certain 
hours of the day, the line pertaining to these motors 
may be placed in the horizontal lines pertaining to the 
hours of the day, as for instance A and B in the figure. 
These two motors never interfere with each other, but 
do occasionally come in at the same time with some of 
the other motors plotted at the bottom of the line. 

Department Stores. — Such places usually require 
large quantities of power for illumination, electric 
signs, and motors. The demand factor for lighting 
is very close to 100 per cent. If economy is not 
too much insisted upon, a bountiful circuit capacity 
should be provided. This will allow brilliant illumi- 
nation wherever it is needed. As department stores 
contain nearly all of the goods handled in other 
stores, hints on illumination of special places should 
be looked up under the corresponding headings — 
dry goods stores, jewelry, etc. As there are usually 
large areas visible from any one place, good appear- 
ance demands some uniform arrangement of fixtures. 
If this does not provide sufficient light for certain 
goods in show cases, local illumination is provided 
in the cases. If branch circuit capacity for five 
watts per square foot is provided, it will enable 
very brilliant illumination of spots without over- 
loading circuits and not interfere with the frequent 
changes which are made. The capacity of general 
mains need not be greater than two watts per square 
foot on the most important flows. 



52 ELECTRICAL TABLES AND DATA 

Depreciation. — Depreciation must be duly consid- 
ered in dealing with, any form of apparatus. The 
depreciation is governed entirely by the useful life 
of the device, but this in turn is governed by the 
amount of wear and tear which cannot be repaired 
for from time to time; obsolescence, possibly in- 
adequacy after a time, or probable cessation of busi- 
ness. Depreciation should not be confused with 
maintenance, to which should be charged all mis- 
haps which, do not permanently lessen the natural 
useful life of the apparatus. From 10 to 20 per cent 
is often charged to depreciation, but it is better to 
estimate it carefully in each case unless a parallel 
case is well understood. 

Desk Lighting. — The illumination of desks by indi- 
vidual lamps is never to be advised, except in the 
case of individuals with very poor eyesight or in 
locations where desks are far apart or used but a 
few hours per day. Where individual desk lighting 
is provided, the cost of energy may sometimes be 
lower, but the first cost of installation, and also 
maintenance, is always high. There is, further, al- 
ways a considerable fire hazard, and all of these 
offset the saving in energy to a large extent. A 
general and fairly shadowless illumination also adds 
much to the efficiency of clerks. The following 
table shows the comparative cost of proper general 
illumination as compared with local for desks of 
various spacing. It is assumed that a general illumi- 
nation of 1J watts per square foot is provided, and 
that at each desk a 25-watt lamp is also used, while 
the general illumination with which this desk light- 
ing is compared is obtained through the medium of 
the most efficient large wattage lamps at present on 
the market. One watt per square foot will give 
good general illumination, which will need to be 
helped out by local lighting only for persons with 



I 



ELECTRICAL TABLES AND DATA 53 

weak eyes. Where local desk lighting is resorted 
to the- wattage requirements will be about as 
follows : 



A v. sq. ft. per desk. . . .20 


25 


30 


35 


40 


45 


50 


Total watts per sq. ft. . 1.5 


1.25 


1.08 


0.96 


0.87 


0.80 


0.75 



It will be noted that where desks are close to- 
gether the general illumination is not only the easiest 
installed but also the cheapest to operate. If the 
desks are used only a small part of the time the 
local illumination will be the cheaper. Lamps used 
for desk lighting should either be frosted or encased 
in diffusing globes. 

Diamagnetic. — Zinc, antimony, bismuth, and cer- 
tain other metals are repelled when placed between 
the poles of strong magnets, and are said to be dia- 
magnetic. Metals which are attracted by magnetism 
are said to be paramagnetic. 

Dielectric. — Any substance which is an insulator 
and allows electrostatic induction to take place 
through its mass. Usually taken as synonymous 
with insulation. 

Dry Kilns. — Such places are too hot for rubber- 
covered wire. Use asbestos-covered. Place cut-outs 
and switches outside. 

Eddy Currents. — Useless currents which are pro- 
duced in the iron of pole pieces, etc., subject to 
. motion in a magnetic field, or to the influence of 
coils in which a fluctuating current exists. They 
cause a waste of energy and heat the metal. 

Efficiency. — The efficiency of motors, transformers, 
and other similar translating devices is found by 
dividing the output by the input. In connection 
with sources of electric illumination the term 
efficiency has an entirely different meaning. The 
efficiency of such devices is spoken of as a certain 



64 ELECTRICAL TABLES AND DATA 

number of watts per candle power. In this case, 
the higher the efficiency, the more uneconomical is 
the lamp. See Motors and Illumination for practical 
applications. 

Egg Candling. — One light must be provided for 
each workman, and it should be located about waist 
high. The wires should be run at this height so 
as to avoid use of long cords. The light is always 
made adjustable, and is encased in a small metallic 
hood with a small opening. 

Electric Braking.— This is also sometimes termed 
" dynamic braking.'' If an electric motor is dis- 
connected from its source of supply, and its arma- 
ture circuit closed while the armature is still in 
motion, it will generate current and consume power, 
and may be brought to rest very quickly in this 
manner. Where the necessary provisions for this 
purpose are installed this method of braking is very 
successful. 

Electrolysis. — Nearly all electrolysis is due to the 
fact that piping and other metallic structures near 
a ground return system of electrical distribution 
afford a return circuit of such low resistance as 
compared to the return circuit provided, that a 
large part of the current returns over the piping. 
It is impossible to prevent electrolysis entirely ex- 
cept by insulating the return wires. The troubles 
may, however, be materially reduced. The current 
does damage only where it leaves the pipes or other 
structures which it has entered, and the damage is 
in proportion to the amperes carried. The methods 
used for lessening electrolysis are the following : 

1. Protection of structures by concrete or other 
forms of insulation, or keeping them as far as pos- 
sible from ground return circuits. Insulation of 
piping is not advisable; it is likely to concentrate 
the trouble at spots where it is poor. 



ELECTRICAL TABLES AND DATA 55 

2. Bonding pipes, etc., so as to prevent current 
which has once entered them from leaving, except 
at predetermined places, and then never to earth. 

3. Negative boosters have been suggested, but 
have not been extensively tried. A negative booster 
is a low-voltage dynamo connected into the return 
circuit in such a manner as to draw current from 
the rails and earth and deliver it back to the sta- 
tion. 

4. Reinforcing the rails, etc., by large conductors, 
thus increasing the conductivity of the return, and 
lowering the p. d. between the rails and the sta- 
tion. 

In most cities ordinances mention the difference 
in- potential which may be allowed to exist between 
any two points on the return wires. In Chicago it 
is provided that all uninsulated electrical return 
circuits must be of such current-carrying capacity 
and so arranged that the difference of potential 
between any two points on the return circuit will 
not exceed the limit of twelve volts, and between 
any two points on the return 1000 feet apart within 
a one-mile radius of the City Hall will not exceed 
the maximum limit of 1 volt, and between any two 
points on the return 700 feet apart outside of this 
one-mile radius limit will not exceed the limit of 1 
volt. In addition thereto, a proper return conductor 
system must be so installed and maintained as to 
protect all metallic work from electrolysis damage. 
The return current amperage on pipes and cable 
sheaths must not be greater than 0.5 amperes per 
pound-foot for caulked cast iron pipe, 8.0 amperes 
per pound-foot for screwed wrought iron pipe, and 
16.0 amperes per pound-foot for standard lead or 
lead alloy sheaths of cables. 

All insulated return current systems must be 
equipped with insulated pilot wire circuits and volt< 



56 ELECTRICAL TABLES AND DATA 

meters, so that accurate chart records will be obtain- 
able daily, showing the difference of potential be- 
tween the negative bus-bars in each station and at 
least four extreme limits on the return circuit in its 
corresponding feeding district. Also with recording 
ammeters, insulated cables, and automatic reverse 
load and overload circuit breakers which will record 
and limit the maximum amperes drained from all 
the metallic work (except the regular return feed- 
ers) to less than 10 per cent of the total output of 
the station. Figuring on the basis of the average 
resistance of cast iron, wrought iron, and lead, the 
above amperages will exist with the following differ- 
ence of potential per running foot, and will be inde- 
pendent of the thickness or size of pipe : Cast iron, 
0.000711 volt per foot ; measurements must be taken 
on solid pipe and not across any joint. Wrought 
iron, 0.001568 volt per foot; measurement to be 
taken as above. Lead sheaths, 0.007497 volt per 
foot; as joints in lead sheaths are always soldered 
and wiped, no attention need be paid to them. The 
lower amperage for the iron piping is specified be- 
cause joints will usually be found of higher resist- 
ance than the piping, and at each joint current is 
likely to leave piping and enter it again just 
beyond. 

The proper treatment of electrolysis may require 
all four methods outlined above. The method most 
to be recommended in a general way is that of re- 
inforcing the return conductors sufficiently to limit 
the difference of potential as prescribed. 

The following table shows the size of copper con- 
ductors necessary with rails of various weights per 
yard to reduce electrolysis to 4, ^, and J, etc.; the 
specific resistance of the rails being taken as 10 
times that of copper, and the resistance of bonds as 
negligible. 



ELECTRICAL TABLES AND DATA 57 

TABLE XV 

Showing e. m. of copper necessary to reduce p. d. 
of electrolysis to the fraction of its original value 



given. 












height o 


f Circular 










Rails Pei 


Mils 


1 


-2 


1-3 


1-4 


Yard 


of Rail 










40 


4,950,000 495,000 


990,000 


1,485.000 


45 


5,600,000 560,000 1,120,000 


1,680,000 


50 


6,230,000 623,000 1 


246,000 


1,869,000 


60 


7,500,000 750,000 1,500,000 


2,250,000 


70 


8,770,000 87 


7,000 1,754,000 


2,631,000 


80 


9,900,000 990,000 1,980,000 


2,970,000 


90 


11,200,000 1,120,000 2,240,000 


3,360,000 


100 


12,500,000 1,250,000 2 


500,000 


3,750,000' 


Weight 


Circular 










of Rails 


Mils 


1-5 


1-6 


1-7 


1-8 


Per Yard 


of Rail 










40 


4,950,000 


1,980,000 


2,475,000 


2,970,000 


3,465,000' 


45 


5,600,000 


2,240,000 


2,800,000 


3,360,000 


3,920,000 


50 


6,230,000 


2,492,000 


3,115,000 


3,738,000 


4,361,000 


60 


7,500,000 


3,000,000 


3,750,000 


4,500,000 


5,250,000 


70 


8,770,000 


3,508,000 


4,385,000 


5,262,000 


6,039,000 


80 


9,900,004 


3,960,000 


4,950,000 


5,940,000 


6,930,000 


90 


11,200,000 


4,480,000 


5,600,000 


6,720,000 


7,840,000 


100 


12,500,000 


5,000,000 


6,250,000 


7,500.000 


8,750,000 



For a comprehensive treatment of electrolysis a map 
of the return circuits and adjacent piping should bo 
made. Tests determining p. d. and direction of cur- 
rent should be made, and results marked upon the 
map. In many cases currents will be found in oppo- 
site direction at the same point at different times. 
In estimating the current strength from p. d. noted 
between track and piping the distance of the latter 
from the track must be taken into consideration. 
If this is small a low p. d. may deliver considerable 
current. Often the trouble can be reduced suffi- 
ciently by running comparatively short lengths of 
heavy copper. In testing p. d.'s it is best to use a- 
sensitive galvanometer. Such an instrument may 
be calibrated with reference to a milli-volt meter. 



58 ELECTRICAL TABLES AND DATA 

TABLE XVI 

The table below shows the approximate amperage 
per milli-volt p.d. per foot which will be found in 
the various kinds and sizes of piping and sheaths 
given. 



Cast Iron, 


Average 


Wrought Iron, 


Average 


Lead Sh 


saths, V a " 


Inside 


wt., 


Am- 


Inside 


wt., 


Am- 


Outside 


Amperes 


Diam. 


Per Ft 


peres 


Diam. 


Per Ft. 


peres 


Diam. 


Approx. 


3 


16 


12 


i 


.87 


4£ 


1.26 


5 


4 


22 


15 


t 


1.15 


5* 


1.50 


6 


6 


35 


25 


l 


1.70 


8 


1.58 


6 


8 


50 


37 


11 


2.25 


11 


1.65 


6.6 


10 


67 


50 


li 


2.75 


14 


1.68- 


6.9 


12 


87 


65 


2 


3.60 


18 


1.72 


7.0 


14 


110 


82 


2i 


5.80 


30 


1.78 


7.1 


16 


135 


102 


3 


7.65 


40 


1.84 


7.2 


18 


165 


123 


3* 


9.00 


48 


1.90 


7.5 


.20 


190 


141 


4 


11.0 


57 


1.95 


7.7 


24 


255 


190 


4i 


12.5 


66 


1.98 


7.9 


30 


370 


275 


5 


15.0 


80 


2.00 


8.0 


36 


500 


375 


6 


19.0 


100 


2.05 


8.2 


42 


665 


500 


7 


24.0 


125 


2.10 


8.4 


48 


850 


635 


8 


29.0 


155 


2.15 


8.6 


54 


1,050 


775 


9 


34.0 


180 


2.19 


8.8 


60 


1,300 


970 


10 


41.0 


220 


2.21 


8.9 


72 


1,575 


1,200 


11 


46.0 


250 


2.24 


9.0 


84 


1,850 


1,400 


12 


51.0 


275 


2.32 


9.3 



Electrolyte is the name given to the solution used 
in storage batteries and other batteries. 

Electromagnets, — The magnetic flux is equal to 
the magnetomotive force divided by the reluctance. 
The magnetomotive force is the product of current 
times number of turns of wire and is known as 
ampere turns. The reluctance of the iron of all well 
designed magnets is very low but that of the air gap 
is high, so that roughly speaking we can judge the 
total reluctance by the air gap. In any given case 
the magnetic flux is approximately proportional to 
the current strength up to a point at which the iron 



ELECTRICAL TABLES AND DATA 5S 

becomes nearly saturated. After this the increase 
is slow until the point of full saturation is reached 
and after this it is very slow. 

To increase the magnetization (e.m. f. being fixed) 
we must increase the size of wire ; winding more turns 
of the same wire upon a spool simply decreases the 
current required for a given magnetization but does 
not alter the magnetization itself. The self-induction 
and the sparking are proportional to the square of 
the number of turns of wire. The heating is pro- 
portional to the square of the current used. The 
heating of the coils sets the limit of the current 
which may be used. A radiating surface of from 
1 to 3 square inches per watt consumed in the coil is 
usually provided. One watt per square inch will 
heat the coil very much if it is in use continuously. 
The possible traction of electromagnets is about 
200 lbs. per square inch for good annealed wrought 
iron, and 75 for cast iron. This, however, varies 
widely with the quality of iron used. In laboratory 
experiments as high as 1,000 lbs. per square inch 
has been obtained. Single phase a-c. magnets do 
not give a constant pull but two and three phase 
magnets are very serviceable. The "chattering" of 
single phase magnets can be lessened by a "shading 
coil." Lifting magnets are extensively used. They 
are built with the two poles concentric and the 
material to be lifted constitutes the armature. Per- 
manent magnets are used only in small sizes. 

USEFUL FORMULAS AND TABLES 

In the following formulas it is assumed that the 
wires lie squarely over one another in the coil, each 
wire fully occupying a space equal to the square of 
its diameter. As in most coils some insulating me- 
dium is placed between the different layers, this is 
about the condition which exists in practice. 



60 



ELECTRICAL TABLES AND DATA 



The symbols used in the formulas are as follows: 

d- diameter of wire, in inches, over insulation. 
I- length of wire, on spool, in inches. 
nt = number of turns. 
r = resistance of one foot of wire. 
rs= radiating surface. 

B = diameter of core and insulation, in inches. 
D = diameter over outside of completed winding, 

in inches. 
L = length of winding space on spool, in inches. 
N - depth of winding from core to outside, in 

inches. 
W = weight of wire. 
a, c,k-= constants for use in the formula, given in the 

tables below. Each constant has a different 

value for each size and kind of wire used. 

Number of turns in a given spool (see Figure 5) : 



m 



z 

_ i _y - -i 

Dm 






Figure 5. 

LxN 



nt 



Diameter of wire to give a certain number of turns : 

d =4 



J LxN 
nt 



ELECTRICAL TABLES AND DATA 61 

Cross-section of winding space, or LxN, necessary 
to accommodate a certain number of turns of a given 
wire : 

LxN -d 2 xnt. 
Length of wire on a given spool : 

1= (D 2 -B 2 ) Lxk. See table below for value of k.. 
"Weight of wire on a given spool : 

W= (D 2 -B 2 ) Lxc. See table below for value of c 
Resistance of wire on a given spool : 

R= (D 2 -B 2 ) Lxa. See table below for value of a.. 
Radiating surface for a given spool : 

rs = DxS.UxL. 



TABLE XVn 
CONSTANTS. 



Constant for Length Constant for Weight Constant for Resistance- 



Pi Q IB CQ H 02 CQ fi OQ «2 

20 40.9 50.4 56.7 .137 .162 .177 .415 .512 .57© 

21 50.4 64.1 72.7 .638 .812 .920 

22 60.2 78.0 89.7 .97 1.257 1.445 

23 68.3 89.7 104.7 1.387 1.82 2.08 

24 83.6 113.5 135. .1115 .149 .169 2.14 2.91 3.46 

25 97.2 135. 163. 3.14 4.36 5.27 

26 114. 163. 202. 4.65 6.65 8.24 

27 135. 202. 255. . 6.94 11.75 13.1 

28 148. 226. 291. .0845 .122 .148 9.60 14.62 18.82 

29 182. 291. 387. - 14.85 23.7 31.6 

30 201. 334. 454. 20.7 34.4 46.8 

31 226. 387. 542. 29.36 50.25 70.4 

32 255. 454. 655. .0687 .1045.132 41.8 74.4 107.2. 

33 291. 542. 812. 60.33 114.5 168. 

34 334. 655. 1023. 87.1 170.5 266.5 

35 354. 712. 1140. 116.2 234. 374.8- 

36 387. 811. 1340. .0492 .0825 .1115 160. 335.5 555. 

37 422. 897. 1582. 220.5 468. 806. 

38 457. 1023. 1825. 308. 674. 1192. 

39 496. 1170. 2165. 412. 972. 1795. 

40 532. 1300. 2525. .038 .0615 .0888 557. 1360. 2645^ 



52 ELECTRICAL TABLES AND DATA 

Depreciation. — Depreciation must be duly consid- 
ered in dealing with any form of apparatus. The 
depreciation is governed entirely by the useful life 
of the device, but this in turn is governed by the 
amount of wear and tear which cannot be repaired 
for from time to time; obsolescence, possibly in- 
adequacy after a time, or probable cessation of busi- 
ness. Depreciation should not be confused with 
maintenance, to which should be charged all mis- 
haps which do not permanently lessen the natural 
useful life of the apparatus. From 10 to 20 per cent 
is often charged to depreciation, but it is better to 
estimate it carefully in each case unless a parallel 
case is well understood. 

Desk Lighting. — The illumination of desks by indi- 
vidual lamps is never to be advised, except in the 
case of individuals with very poor eyesight or in 
locations where desks are far apart or used but a 
few hours per day. Where individual desk lighting 
is provided, the cost of energy may sometimes be 
lower, but the first cost of installation, and also 
maintenance, is always high. There is, further, al- 
ways a considerable fire hazard, and all of these 
offset the saving in energy to a large extent. A 
general and fairly shadowless illumination also adds 
much to the efficiency of clerks. The following 
table shows the comparative cost of proper general 
illumination as compared with local for desks of 
various spacing. It is assumed that a general illumi- 
nation of 1J watts per square foot is provided, and 
that at each desk a 25-watt lamp is also used, while 
the general illumination with which this desk light- 
ing is compared is obtained through the medium of 
the most efficient large wattage lamps at present on 
the market. One watt per square foot will give 
good general illumination, which will need to be 
helped out by local lighting only for persons with 



ELECTRICAL TABLES AND DATA 53 

weak eyes. Where local desk lighting is resorted 
to the- wattage requirements will be about as 
follows : 

Av. sq. ft. per desk 20 25 30 35 40 45 50 

Total watts per sq. ft. 1.5 1.25 1.08 0.96 0.87 0.80 0.75 

It will be noted that where desks are close to- 
gether the general illumination is not only the easiest 
installed but also the cheapest to operate. If the 
desks are used only a small part of the time the 
local illumination will be the cheaper. Lamps used 
for desk lighting should either be frosted or encased 
in diffusing globes. 

Diamagnetic. — Zinc, antimony, bismuth, and cer- 
tain other metals are repelled when placed between 
the poles of strong magnets, and are said to be dia- 
magnetic. Metals which are attracted by magnetism 
are said to be paramagnetic. 

Dielectric. — Any substance which is an insulator 
and allows electrostatic induction to take place 
through its mass. Usually taken as synonymous 
with insulation. 

Dry Kilns. — Such places are too hot for rubber- 
covered wire. Use asbestos-covered. Place cut-outs 
and switches outside. 

Eddy Currents. — Useless currents which are pro- 
duced in the iron of pole pieces, etc., subject to 
. motion in a magnetic field, or to the influence of 
coils in which a fluctuating current exists. They 
cause a waste of energy and heat the metal. 

Efficiency. — The efficiency of motors, transformers, 
and other similar translating devices is found by 
dividing the output by the input. In connection 
with sources of electric illumination the term 
efficiency has an entirely different meaning. The 
efficiency of such devices is spoken of as a certain 



64 ELECTRICAL TABLES AND DATA 

number of watts per candle power. In this case, 
the higher the efficiency, the more uneconomical is 
the lamp. See Motors and Illumination for practical 
applications. 

Egg Candling. — One light must be provided for 
each workman, and it should be located about waist 
high. The wires should be run at this height so 
as to avoid use of long cords. The light is always 
made adjustable, and is encased in a small metallic 
hood with a small opening. 

Electric Braking.— This is also sometimes termed 
"dynamic braking.' ' If an electric motor is dis- 
connected from its source of supply, and its arma- 
ture circuit closed while the armature is still in 
motion, it will generate current and consume power, 
and may be brought to rest very quickly in this 
manner. Where the necessary provisions for this 
purpose are installed this method of braking is very 
successful. 

Electrolysis. — Nearly all electrolysis is due to the 
fact that piping and other metallic structures near 
a ground return system of electrical distribution 
afford a return circuit of such low resistance as 
compared to the return circuit provided, that a 
large part of the current returns over the piping. 
It is impossible to prevent electrolysis entirely ex- 
cept by insulating the return wires. The troubles 
may, however, be materially reduced. The current 
does damage only where it leaves the pipes or other 
structures which it has entered, and the damage is 
in proportion to the amperes carried. The methods 
used for lessening electrolysis are the following : 

1. Protection of structures by concrete or other 
forms of insulation, or keeping them as far as pos- 
sible from ground return circuits. Insulation of 
piping is not advisable; it is likely to concentrate 
the trouble at spots where it is poor. 






ELECTRICAL TABLES AND DATA 55 

2. Bonding pipes, etc., so as to prevent current 
which has once entered them from leaving, except 
at predetermined places, and then never to earth. 

3. Negative boosters have been suggested, but 
have not been extensively tried. A negative booster 
is a low-voltage dynamo connected into the return 
circuit in such a manner as to draw current from 
the rails and earth and deliver it back to the sta- 
tion. 

4. Reinforcing the rails, etc., by large conductors, 
thus increasing the conductivity of the return, and 
lowering the p. d. between the rails and the sta- 
tion. 

In most cities ordinances mention the difference 
in- potential which may be allowed to exist between 
any two points on the return wires. In Chicago it 
is provided that all uninsulated electrical return 
circuits must be of such current-carrying capacity 
and so arranged that the difference of potential 
between any two points on the return circuit will 
not exceed the limit of twelve volts, and between 
any two points on the return 1000 feet apart within 
a one-mile radius of the City Hall will not exceed 
the maximum limit of 1 volt, and between any two 
points on the return 700 feet apart outside of this 
one-mile radius limit will not exceed the limit of 1 
volt. In addition thereto, a proper return conductor 
system must be so installed and maintained as to 
protect all metallic work from electrolysis damage. 
The return current amperage on pipes and cable 
sheaths must not be greater than 0.5 amperes per 
pound-foot for caulked cast iron pipe, 8.0 amperes 
per pound-foot for screwed wrought iron pipe, and 
16.0 amperes per pound-foot for standard lead or 
lead alloy sheaths of cables. 

All insulated return current systems must be 
equipped with insulated pilot wire circuits and volt< 



56 ELECTRICAL TABLES AND DATA 

meters, so that accurate chart records will be obtain- 
able daily, showing the difference of potential be- 
tween the negative bus-bars in each station and at 
least four extreme limits on the return circuit in its 
corresponding feeding district. Also with recording 
ammeters, insulated cables, and automatic reverse 
load and overload circuit breakers which will record 
and limit the maximum amperes drained from all 
the metallic work (except the regular return feed- 
ers) to less than 10 per cent of the total output of 
the station. Figuring on the basis of the average 
resistance of cast iron, wrought iron, and lead, the 
above amperages will exist with the following differ- 
ence of potential per running foot, and will be inde- 
pendent of the thickness or size of pipe : Cast iron, 
0.000711 volt per foot ; measurements must be taken 
on solid pipe and not across any joint. "Wrought 
iron, 0.001568 volt per foot; measurement to be 
taken as above. Lead sheaths, 0.007497 volt per 
foot; as joints in lead sheaths are always soldered 
and wiped, no attention need be paid to them. The 
lower amperage for the iron piping is specified be- 
cause joints will usually be found of higher resist- 
ance than the piping, and at each joint current is 
likely to leave piping and enter it again just 
beyond. 

The proper treatment of electrolysis may require 
all four methods outlined above. The method most 
to be recommended in a general way is that of re- 
inforcing the return conductors sufficiently to limit 
the difference of potential as prescribed. 

The following table shows the size of copper con- 
ductors necessary with rails of various weights per 
yard to reduce electrolysis to -J, f, and ^, etc.; the 
specific resistance of the rails being taken as 10 
times that of copper, and the resistance of bonds as 
negligible. 



ELECTRICAL TABLES AND DATA 57 

TABLE XV 

Showing e. m. of copper necessary to reduce p. d. 
of electrolysis to the fraction of its original value 
given. 



height of Circular 










Rails Per 


Mils 


1 


-2 


1-3 


1-4 


Yard 


of Rail 










40 


4,950,000 


49 


5,000 


990,000 


1,485.000 


45 


5,600,000 


560,000 1,120,000 


1,680,000 


50 


6,230,000 


623,000 1 


246,000 


1,869,000 


60 


7,500,000 


75 


1,000 1,500,000 


2,250,000 


70 


8,770,000 


877,000 1 


754,000 


2,631,000 


80 


9,900,000 


990,000 1,980,000 


2,970,000 


90 


11,200,000 


1,120,000 2,240,000 


3,360,000 


100 


12,500,000 


1,250,000 2 


500,000 


3,750,000' 


Weight 


Circular 










of Rails 


Mils 


1-5 


1-6 


1-7 


1-8 


Per Yard 


of Rail 










40 


4,950,000 1,980,000 


2,475,000 


2,970,000 


3,465,000' 


45 


5,600,000 2,240,000 


2,800,000 


3,360,000 


3,920,000 


50 


6,230,000 2,492,000 


3,115,000 


3,738,000 


4,361,000 


60 


7,500,000 3,000,000 


3,750,000 


4,500,000 


5,250,000 


70 


8,770,000 3 


508,000 


4,385,000 


5,262,000 


6,039,000 


80 


9,900,00D 3,960,000 


4,950,000 


5,940,000 


6,930,000 


90 


11,200,000 4,480,000 


5,600,000 


6,720,000 


7,840,000 


100 


12,500,000 5,000,000 


6,250,000 


7,500,000 


8,750,000 



For a comprehensive treatment of electrolysis a map 
of the return circuits and adjacent piping should be 
made. Tests determining p. d. and direction of cur- 
rent should be made, and results marked upon the- 
map. In many cases currents will be found in oppo- 
site direction at the same point at different times. 
In estimating the current strength from p. d. noted 
between track and piping the distance of the latter 
from the track must be taken into consideration. 
If this is small a low p. d. may deliver considerable 
current. Often the trouble can be reduced suffi- 
ciently by running comparatively short lengths of 
heavy copper. In testing p. d.'s it is best to use a- 
sensitive galvanometer. Such an instrument may 
be calibrated with reference to a milli-volt meter. 



58 ELECTRICAL TABLES AND DATA 

TABLE XVI 

The table below shows the approximate amperage 
per milli-volt p.d. per foot which will be found in 
the various kinds and sizes of piping and sheaths 
given. 



Cast Iron, 


Average 


Wrought Iron, 


Average 


Lead Sheaths, %" 


Inside 


wt., 


Am- 


Inside 


wt., 


Am- 


Outside 


Amperes 


Diam. 


Per Ft 


peres 


Diam. 


Per Ft. 


peres 


Diam. 


Approx. 


3 


16 


12 


1 


.87 


4£ 


1.26 


5 


4 


22 


15 


1 


1.15 


5* 


1.50 


6 


6 


35 


25 


1 


1.70 


8 


1.58 


6 


8 


50 


37 


n 


2.25 


11 


1.65 


6.6 


10 


67 


50 


li 


2.75 


14 


1.68- 


6.9 


12 


87 


65 


2 


3.60 


18 


1.72 


7.0 


14 


110 


82 


2J 


5.80 


30 


1.78 


7.1 


16 


135 


102 


3 


7.65 


40 


1.84 


7.2 


18 


165 


123 


3* 


9.00 


48 


1.90 


7.5 


.20 


190 


141 


4 


11.0 


57 


1.95 


7.7 


24 


255 


190 


4i 


12.5 


66 


1.98 


7.9 


30 


370 


275 


5 


15.0 


80 


2.00 


8.0 


.36 


500 


375 


6 


19.0 


100 


2.05 


8.2 


42 


665 


500 


7 


24.0 


125 


2.10 


8.4 


48 


850 


635 


8 


29.0 


155 


2.15 


8.6 


54 


1,050 


775 


9 


34.0 


180 


2.19 


8.8 


60 


1,300 


970 


10 


41.0 


220 


2.21 


8.9 


72 


1,575 


1,200 


11 


46.0 


250 


2.24 


9.0 


84 


1,850 


1,400 


12 


51.0 


275 


2.32 


9.3 



Electrolyte is the name given to the solution used 
in storage batteries and other batteries. 

Electromagnets. — The magnetic flux is equal to 
the magnetomotive force divided by the reluctance. 
The magnetomotive force is the product of current 
times number of turns of wire and is known as 
ampere turns. The reluctance of the iron of all well 
designed magnets is very low but that of the air gap 
is high, so that roughly speaking we can judge the 
total reluctance by the air gap. In any given case 
the magnetic flux is approximately proportional to 
the current strength up to a point at which the iron 



ELECTRICAL TABLES AND DATA 5S 

becomes nearly saturated. After this the increase 
is slow until the point of full saturation is reached 
and after this it is very slow. 

To increase the magnetization (e.m. f. being fixed) 
we must increase the size of wire ; winding more turns 
of the same wire upon a spool simply decreases the 
current required for a given magnetization but does 
not alter the magnetization itself. The self-induction 
and the sparking are proportional to the square of 
the number of turns of wire. The heating is pro- 
portional to the square of the current used. The 
heating of the coils sets the limit of the current 
which may be used. A radiating surface of from 
1 to 3 square inches per watt consumed in the coil is 
usually provided. One watt per square inch will 
heat the coil very much if it is in use continuously. 
The possible traction of electromagnets is about 
200 lbs. per square inch for good annealed wrought 
iron, and 75 for cast iron. This, however, varies 
widely with the quality of iron used. In laboratory 
experiments as high as 1,000 lbs. per square inch 
has been obtained. Single phase a-c. magnets do 
not give a constant pull but two and three phase 
magnets are very serviceable. The "chattering" of 
single phase magnets can be lessened by a "shading 
coil." Lifting magnets are extensively used. They 
are built with the two poles concentric and the 
material to be lifted constitutes the armature. Per- 
manent magnets are used only in small sizes. 

USEFUL FORMULAS AND TABLES 

In the following formulas it is assumed that the 
wires lie squarely over one another in the coil, each 
wire fully occupying a space equal to the square of 
its diameter. As in most coils some insulating me- 
dium is placed between the different layers, this is 
about the condition which exists in practice. 



60 



ELECTRICAL TABLES AND DATA 



The symbols used in the formulas are as follows: 

d= diameter of wire, in inches, over insulation. 
I- length of wire, on spool, in inches. 
nt = number of turns. 
r = resistance of one foot of wire. 
rs= radiating surface. 

B = diameter of core and insulation, in inches. 
D = diameter over outside of completed winding, 

in inches. 
L =s length of winding space on spool, in inches. 
N - depth of winding from core to outside, in I 

inches. 
W = weight of wire. 
a, c,k- constants for use in the formula, given in the 

tables below. Each constant has a different 

value for each size and kind of wire used. 

Number of turns in a given spool (see Figure 5) : 







Figure 5. 



nt-. 



LxN 



Diameter of wire to give a certain number of turns : 



ELECTRICAL TABLES AND DATA 61 

Cross-section of winding space, or LxN, necessary 
to accommodate a certain number of turns of a given 
wire : 

LxN = d 2 x nt. 
Length of wire on a given spool : 

I- (D 2 -B 2 ) Lxk. See table below for value of k.. 
Weight of wire on a given spool : 

W= (D 2 -B 2 ) Lxc. See table below for value of cS 
Resistance of wire on a given spool : 

B - (D 2 - B 2 ) L x a. See table below for value of a„ 
Radiating surface for a given spool : 

rs = DxZ.14:xL. 



TABLE XVII 
CONSTANTS. 



Constant for Length Constant for Weight Constant for Resistance- 



20 


40.9 


50.4 


56.7 


.137 


.162 


.177 


.415 


.512 


.57© 


21 


50.4 


64.1 


72.7 








.638 


.812 


.920 


22 


60.2 


78.0 


89.7 








.97 


1.257 


1.445 


23 


68.3 


89.7 


104.7 








1.387 


1.82 


2.08 


24 


83.6 


113.5 


135. 


.1115 


.149 


.169 


2.14 


2.91 


3.46 


25 


97.2 


135. 


163. 








3.14 


4.36 


5.27 


26 


114. 


163. 


202. 








4.65 


6.65 


8.24 


27 


135. 


202. 


255. 








. 6.94 


11.75 


13.1 


28 


148. 


226. 


291. 


.0845 


.122 


.148 


9.60 


14.62 


18.82-' 


29 


182. 


291. 


387. 








14.85 


23.7 


31.6 


30 


201. 


334. 


454. 








20.7 


34.4 


46.8 


31 


226. 


387. 


542. 








29.36 


50.25 


70.4 


32 


255. 


454. 


655. 


.0687 


.1045 


.132 


41.8 


74.4 


107.2, 


33 


291. 


542. 


812. 








60.33 


114.5 


168. 


34 


S34. 


655. 


1023. 








87.1 


170.5 


266.5 


35 


354. 


712. 


1140. 








116.2 


234. 


374.8- 


36 


387. 


811. 


1340. 


.0492 


.0825 


.1115 


160. 


335.5 


555. 


37 


422. 


897. 


1582. 








220.5 


468. 


806. 


38 


457. 


1023. 


1825. 








308. 


674. 


1192. 


39 


496. 


1170. 


2165. 








412. 


972. 


1795. 



40 532. 1300. 2525. .038 .0615 .0888 557. 



ELECTRICAL TABLES AND DATA 

TABLE XVLTI 

Round Cotton-covered Magnet Wire 

American Steel & Wire Co. 

Coarse Sizes 





55 


Allowable 

Variation 

Either 

"Way in 

Per Cent. 


Rated 
Area 

in Cir. 
Mils. 


Cov'ered Approxi- 
mate Values 

Outside Feet 
Diameter per 

Inches Pound 


Covered Approx 
imate Values 
Outside Feet 

Diameter per 
Inches Poun 





0.3249 


£ofl 


105,625 


.333 


3.1 


.339 


3.1 


l 


.2893 


iof 1 


83,694 


.297 


3.9 


.303 


3.9^ 


2 


.2576 


lofl 


66,358 


.266 


5. 


.272 


4.9 


3 


.2294 


fofl 


52,624 


.237 


6.2 


.243 


6.2 


4 


.2043 


fofl 


41,738 


.212 


7.8 


.218 


7.8 


5 


/ 

.1819 


f ofl 


33,088 


.190 


9.9 


.196 


9.9 


6 


.1620 


fofl 


26,244 


.170 


12.5 


.176 


12.4 


7 


.1443 


fofl 


20,822 


.152 


15.7 


.158 


15.6 


8 


.1285 


1 


16,512 


.136 


19.8 


.142 


19.6 


9 


.1144 


1 


13,087 


.121 


24.9 


.125 


24.7 


10 


.1019 


1 


10,384 


.108 


31.4 


.113 


31.1 


11 


.0907 


1 


8,226 


.097 


39.5 


.102 


39.1 


12 


.0808 


n 


6,528 


.087 


49.6 


.092 


49.2 


13 


.0720 


H 


5,184 


.078 


62.5 


.083 


61.7 


14 


.0641 


H 


4,108 


.070 


78.6 


.075 


77.5 


15 


.0571 


1* 


3,260 


.063 


98.9 


.068 


97 


16 


.0508 


1* 


2,580 


.056 


125 


.060 


122 


17 


.0453 


11 


2,052 


.050 


157 


.054 


153 


18 


.0403 


1* 


1,624 


.045 


198 


.050 


192 


19 


.0359 


If 


1,288 


.041 


248 


.045 


240 



ELECTRICAL TABLES ANp DATA 



ENAMELED MAGNET WIRE 

Enamel insulation has a dielectric strength far in 
excess of silk or cotton covered wire. It will also 
withstand a much greater heat, as silk and cotton 
insulation will char at 270° Fahr., whereas enamel 
insulation will withstand 450° Fahr. without the 
slightest deterioration. 

Another decided feature about enamel insulation 
is the economy of space where this material is used 
for coil windings, and it takes up much less space 
than the single silk insulation. This feature is a 
very important one, especially to manufacturers of 
electrical instruments and apparatus where space 
economy is essential. 



TABLE XIX 



m 

acM Diam. Approx. Approx. Dlam. Approx. Approx. 

n . Enam. Feet Turns per Size Enam. Feet Turns per- 

izjffl Wire per Lb. Sq. In. B. & S. Wire per Lb. Sq. In. 

16 126 359 29 .0122 2570 7900 

17 159 447 30 .0109 3240 10000 

18 .... 201 567 31 .0097 4082 12620 

19 .... 253 715 32 .0087 5132 16020 

20 .0337 320 885 33 .0077 6445 20400 

21 .0302 404 1126 34 .0069 8093 25200 

22 .0269 509 1400 35 .0062 10197 31900 

23 .0241 642 1736 36 .0055 12813 40000 

24 .0215 810 2160 37 .0049 16110 51600 

25 .0192 1019 2770 38 .0044 20274 65700 

26 .0171 1286 3460 39 .0039 25519 81600 

27 .0153 1620 4270 40 .0035 32107 104000 

28 .0136 2042 5400 * 



<64 



ELECTRICAL TABLES AND DATA 



TABLE XX 



Table for Insulated Copper Wire. (Belden Manufacturing Co.) 



Single Cotton, Double Cotton, Single Silk, Double Silk, 

Total Insulation Total Insulation Total Insulation Total Insulation 





Thickness 
4 Mils. 


Thickness 
8 Mils. 


Thickness 
1% Mils. 


Thickness 
4 Mils. 


21 


Ohms 

per 
pound 


Feet Ohms 

per per 

pound pound 


Feet 

per 

pound 


Ohms 

per 
pound 


Feet 

per 

pound 


Ohms 

per 
pound 


Feet 
per 
pound 


20 


3.15 


311 


3.02 


298 


3.24 


319 


3.18 


312 


21 


4.99 


389 


4.72 


370 


5.12 


403 


5.03 


389 


22 


7.88 


488 


7.44 


461 


8.15 


503 


7.96 


493 


23 


12.44 


612 


11.7 


584 


12.92 


636 


12.65 


631 


24 


19.55 


762 


18.25 


745 


20.50 


800 


19.95 


779 


25 


30.8 


957 


28.45 


903 


32.50 


1005 


31.5 


966 


26 


48.6 


1192 


44.3 


1118 


51.29 


1265 


49.7 


1202 


27 


76.45 


1488 


68.8 


1422 


82.00 


1590 


78.3 


1542 


:28 


120. 


1852 


106.5 


1759 


129.00 


1972 


123.5 


1917 


29 


188.5 


2375 


164. 


2207 


205.00 


2570 


194. 


2485 


30 


294.6 


2860 


252. 


2534 


328.5 


3145 


306.5 


2909 


31 


460.5 


3800 


384.5 


2768 


512.3 


3943 


477. 


3683 


32 


716. 


4375 


585. 


3737 


810.0 


4950 


747. 


4654 


33 


1117. 


5390 


880. 


4697 


1277.5 


6180 


1165. 


5689 


34 


1720. 


6580 


1315. 


6168 


2018. 


7740 


1810. 


7111 


35 


2642. 


8050 


1960. 


6737 


3175. 


9680 


2820. 


8534 


36 


4060. 


9820 


2890. 


7877 


4970. 


12000 


4340. 


10039 


37 


6190. 


11860 


4230. 


9309 


7940. 


15000 


6660. 


10666 


38 


9440. 


14300 


6150. 


10666 12320. 


18660 10250. 


14222 


39 


14420. 


17130 


8850. 


11907 19200. 


23150 15600. 


16516 


40 


22600. 


21590 12500. 


14222 30200. 


28700 23650. 


21333 



ELECTRICAL TABLES AND DATA 



TABLE XXI 

Table of Diameters (d) and Square of Diameters (d2) fop 
Insulated Copper Wire. 



\.&s. 


Double 


) Cotton 


Singh 


Cotton 


Single Silk 




d 


d2 


d 


d2 


d 


d2 


20 


.040 


.0016 


.036 


.001296 


.034 


.001156 


21 


.036 


.0013 


.032 


.00102 


.030 


.0009 


22 


.033 


.00109 


.029 


.00084 


.027 


.00073 


23 


.031 


.00096 


.027 


.00073 


.025 


.000625 


24 


.028 


.000784 


.024 


.000576 


.022 


.000484 


25 


.026 


.000675 


.022 


.000484 


.020 


.0004 


26 


.024 


.000575 


.020 


.0004 


.018 


.000324 


27 


.022 


.000484 


.018 


.000324 


.016 


.000256 


28 


.021 


.000441 


.017 


.000289 


.015 


.000225 


29 


.019 


.00036 


.015 


.000225 


.013 


.000169 


30 


.018 


.000324 


.014 


.000196 


.012 


.000144 


31 


.017 


.000289 


.013 


.000169 


.011 


.000121 


32 


.016 


.000256 


.012 


.000144 


.010 


.000100 


33 


.015 


.000225 


.011 


.000121 


.009 


.000081 


34 


.014 


.000196 


.010 


.000100 


.008 


.000064 


35 


.0136 


.000185 


.0096 


.000092 


.0076 


.0000576 


36 


.013 


.000169 


.009 


.000081 


.007 


.000049 


37 


.0124 


.000155 


.00845 


.000073 


.00645 


.0000415 


38 


.012 


.000143 


.008 


.000064 


.006 


.0000362 


39 


.0115 


.000132 


.0075 


.000056 


.0055 


.0000303 


40 


.0111 


.000123 


.0071 


.0000504 


.0051 


.000025 



66 ELECTRICAL TABLES AND DATA 

Elevators. — Electric motors are used direct con- 
nected or belted; in some cases they are used to 
pump water for hydraulic elevators. Motors should 
be capable of exerting a strong starting torque, and 
are generally compounded. Means are usually pro- 
vided for cutting out the compound winding, or 
otherwise weakening the field to obtain high speeds. 
To prevent sparking at the brushes, commutating 
poles are frequently used. The ordinary commer- 
cial motor is seldom used for elevator service. 

The methods of speed control with d. c. motors 
consist in weakening the field and cutting resistance 
out or in; dynamic braking is also used in some 
cases for slowing down. With a. c. motors wound 
rotors are often used. 

Single phase as well as two and three phase motors 
are practicable, and variable speed motors are often 
employed. Hydraulic elevators require about 1.7 as 
much power as direct connected. A.-c. elevator 
motors under the same conditions require about 20 
to 30 per cent more power than d. c. motors. 

The H. P. required can be found by the formula 

33,000xe 

where 1 = unbalanced load in pounds, 5 = speed in feet 
per mmute, e = combined efficiency of motor and ele- 
vator machinery. This is usually about 0.50. 

The speed of freight elevators often runs as low 
as 65 to 85 feet per minute, while some passenger 
elevators run as fast as 700 feet per minute. As 
the load is always intermittent motors may be rated 
high, and the starting torque is from two to two 
and one-half times running torque. 

The following table gives the H. P. required to lift 
various loads at speeds given ; a combined efficiency 
of 50 per cent being assumed. 



ELECTRICAL TABLES AND DATA 



TABLE XXII 

Table showing H. P. required to lift unbalanced loads at 
~.s given. Efficiency of 50 per cent assumed. 

in Feet Per Minute 



Lbs. 


75 


100 


125 


150 


200 


250 


300 


400 


500 


1000... 


4.5 


6.1 


7.6 


9.1 


12.1 


15.1 


18.2 


24.2 


30.2 


1250... 


5.7 


7.6 


9.5 


11.4 


15.2 


19.0 


22.8 


30.4 


38.0 


1500... 


6.8 


9.1 


11.4 


13.6 


18.2 


22.8 


27.2 


36.4 


45.6 


1750... 


7.9 


10.5 


13.3 


15.8 


21.0 


26.6 


31.6 


42.0 


53.2 


2000. . . 


9.1 


12.1 


15.2 


18.2 


24.2 


30.4 


36.4 


48.4 


60.8 


2500... 


11.3 


15.1 


19.0 


22.6 


30.2 


38.0 


45.2 


60.4 


76.0 


3000... 


13.6 


18.2 


23.7 


27.2 


36.4 


47.4 


54.4 


72.8 


94.8 


3500... 


15.9 


21.2 


27.5 


31.8 


42.4 


55.0 


63.6 


84.8 


110.0 


4000... 


18.2 


24.2 


30.4 


36.4 


48.4 


60.8 


72.8 


96.8 


121.6 


4500... 


20.4 


27.3 


34.2 


40.8 


54.6 


68.4 


81.6 


109.2 


136.8 


5000... 


22.7 


30.3 


38.0 


45.4 


60.6 


76.0 


90.8 


121.2 


152.0 


6000... 


27.2 


36.4 


45.4 


54.4- 


72.8 


90.8 


108.8 


145.6 


181.6 



Emergency Lighting. — This is usually required in 
churches, theatres and other places where large num- 
bers of people congregate. The purpose is to pro- 
vide a system of illumination which shall be in 
service if the main system should fail. In large 
cities the emergency lighting is supposed to be used 
during the entire time the audience is in the build- 
ing. An entirely independent and separate service 
should be provided for it, and there should be no 
switches or fuses except those absolutely necessary. 

Equalisers. — Equalizer wires are used in connec- 
tion with two or more compound generators operated 
in parallel. All connections must be to the same 
terminal with series field. Wires should be led to 
switchboard, and connected to middle blade of 
switch. Arrange switch blades so that equalizer 
will be connected slightly ahead of other wire. 
The lower the resistance of the equalizer, the closer 
will be the regulation of the machines. Never con- 
nect ammeter on same side with equalizer. 



68 ELECTRICAL TABLES AND DATA 

Factors. — Assurance Factor.— This is the ratio of 
the voltage at which a wire or cable is tested to that 
at which it is to be used. 

Demand Factor. (See Demand Factor). — This is 
the ratio or the maximum demand of any system, or 
part of a system, to the total connected load of the 
system, or of the part of the system under consider- 
ation. 

Diversity Factor. — The diversity factor of any 
part of a system of distribution is the ratio of the 
sum of the maxima of the subdivisions to the maxi- 
mum demand on the source of supply during some 
given time. 

To find the diversity factor we divide the sum of 
the maxima of the consumers during a given period 
of time by the maximum registered at the source of 
supply during the same time. If all consumers use 
their maximum energy at the same instant the diver- 
sity factor is 1. A large diversity factor is a dis- 
tinct advantage. In a central station system a cer- 
tain diversity factor will be found to exist between 
the consumers maxima, and the transformer serving 
them; between the various transformers and the 
main serving them there will be another diversity 
factor; between the mains and their feeder still 
another will exist, and so on between mains, sub- 
stations, transmission lines, and central station. The 
diversity factor of the last station is found by multi- 
plying together all the other diversity factors. 

Average diversity factors for a large central sta- 
tions as given by Gear & Williams are : 

Residence lighting. Diversity factor from 3.32 to 
3.40. Commercial lighting. Diversity factor from 
1.40 to 1.51. General power. Diversity factor from 
1.39 to 1.60. 

Load Factor. — The load factor is the ratio of the 
average load to the maximum load demanded by a 



ELECTRICAL TABLES AND DATA 6& 

consumer, a group of consumers connected to a sin- 
gle transformer, a group of transformers, feeders, 
mains, transmission lines, substations, generators, or 
central stations. For each of these on the same sys- 
tem it has a different value which is found by divid- 
ing the average load by the maximum load. A low 
load factor is a disadvantage. 

The following data are condensed from fables pub- 
lished by Gear & Williams in ' ' Electric Central Sta- 
tion Distributing Systems." 

Eesidence lighting. 

Individual consumer's average load factor =7%. 
Transformer load factor = 23% to 24%. 

Commercial lighting. 
Average consumer's load factor = 10% to 13%. 
Transformer load factor = 15% to 19%. 

General power. 
Average consumer's load factor = 15% to 21%. 
Transformer load factor =21% to 30%. 

Plant Factor. — This is the ratio of the average load 
to /the rated capacity of the power plant. 

Power Factor. — The power factor is the ratio of 
the true power to the volt-amperes. In the case of 
sinusoidal voltage and current, the power factor is 
equal to the cosine of their difference in phase. The 
power factor is always less than unity and may be 
either lagging or leading. 

Reactance Factor. — This is the ratio existing be- 
tween the reactance of a circuit, and its ohmic resist- 
ance. 

Reactive Factor. — The reactive factor expresses 
the ratio of the wattless volt-amperes to the total 
volt-amperes. It is equal to the reactance divided by 
the impedance, which is equal to the sine of the 
angle between the impressed voltage and the current. 

Safety Factor.-^-The ratio of the strength of ma- 
terial to the load to which it is to be subjected. It is 



70 ELECTRICAL TABLES AND DATA 

common practice to use a safety factor of 4 or 5. 

Saturation Factor. — The saturation factor of a ma- 
chine is the ratio of a small percentage increase in 
the field excitation, to the corresponding increase in 
voltage thereby produced. 

Factories. — It is an old custom to illuminate fac- 
tories by means of small c. p. lamps distributed among 
machinery so as to give each workman in need of it 
one lamp. Since the advent of the large wattage 
tungsten, or Mazda lamps, this has been somewhat 
changed. The change has been further helped along 
by individual drive machinery which has eliminated 
the belting and shafting. Where the work is not 
particular, one 100 watt tungsten lamp, if kept clean, 
to every 200 or 300 square feet of floor surface will 
give good results. Where particular work is done 
this illumination must be helped out by a 15 watt 
local lamp. A general illumination has the advan- 
tage that it will not have to be changed every time a 
machine is moved, which frequently happens. Where 
individual lighting for machinery is to be provided 
it will be well to avoid placing lamps before the 
machinery is located ; plans are seldom reliable. The 
mercury vapor lamp gives a very serviceable illumin- 
ation for some purposes, but it is said that fine ma- 
chine work is not well done under it ; also because of 
the ghastly appearance is gives faces, many men do 
not like to work under it. Oil dissolves rubber very 
fast, and when flexible cord is used around machinery 
it is well to encase it in loom. 

To avoid interference with open wires run them as 
far as possible between joists or along beams. Drop 
all lights from ceiling and never use floor pockets or 
side wall outlets. Make ample provision for glue 
pots and small portable motors. 

(For hints on motors, see Motors.) 

Fans. — (See Ventilation.) 



ELECTRICAL TABLES AND DATA 71 

Farad. — The practical unit of capacity. A con- 
denser or conductor in which a charge of one coulomb 
(1 ampere for 1 second) produces a p. d. of one volt 
has a capacity of one farad. The farad is much too 
large for practical work, and micro-farads' are used. 
A condensor of two or three micro-farads is quite 
large. 

Faradic Current. — This term is used in therapeu- 
tics, and designates the current taken from an induc- 
tion coil as distinguished from a galvanic or direct 
t-.urrent. 

Faure Plate. — In this type of storage battery plate, 
the active material is pasted onto the supporting 
material, instead of being formed there. This type 
of plate is used mostly for vehicles. It gives a maxi- 
mum of capacity with a minimum of weight. 

Feeders. — These are the wires which start from a 
central station, substation, or other center and feed a 
group or center from which mains supply translating 
devices. The term is always rather loosely used. 
There may be feeders and sub-feeders. A voltage of 
about 1,000 per mile of feeder length is customary. 

Festoons. — Festoons to be strung across streets are 
usually wired with number 8 or 10 wire, and weather- 
proof sockets. As a rule they are supported in the 
center of the street, and swung from pulleys which 
allow of lowering for lamp renewals, etc. In order 
to allow for graceful hanging the wires should be 
from 1.3 to 1.6 times the width of street. Lights are 
usually spaced from 18 inches to two feet apart. At 
street intersections two festoons are often swung 
diagonally across, and in such a case the length of 
wire should be two times the width of street. The 
supporting cables from which the festoons are swung 
are attached to buildings and poles on opposite side 
of street and in many cases they must be run diag- 
onally to find attachments which will allow the fes- 



72 ELECTRICAL TABLES AND DATA 

toon to come in its proper place. This often necessi- 
tates very long spans and requires strong cables. 
Three-eighths and half-inch steel cables are often 
used. Where festoons are swung over trolley lines 
strain insulators are used. Festoons for theatre 
work are made up of stage cable and weatherproof 
sockets; joints are staggered, and taped to prevent 
strain on joints. 

Fiber. — This, in general, is a serviceable insulating 
material, but on account of the fact that it does not 
resist moisture, and swells and warps when wet, it 
is not approved for light and power voltages. 

Field.— This term describes either a magnetic, or 
an electrostatic field. Field magnets are the electro- 
magnets which produce the electric field in which the 
armature revolves. Field coils are the coils in which 
the magnetizing current circulates. A field rheostat 
is one which regulates the current in the field coils. 
A field of force is the space traversed by an electro- 
static, or magnetic flux. The field windings of induc- 
tion motors are those in which the rotating field is 
produced. 

Fire Alarms. — May be either automatically, or 
manually operated. In the manual system a glass 
disk is usually broken to send in an alarm. In the 
automatic system a fuse opens, or closes a circuit 
and sends in the alarm. A system in which the cur- 
rent is constantly flowing is always preferable be- 
cause it is always under test, and failure of any kind 
will send in an alarm. Means of testing without 
sending in alarms should be provided. The common 
fire alarm telegraph system consists of boxes con- 
taining notched wheels which are released when the 
box is pulled, and send in the code signal. 

Fish Work. — For light and power voltages ar- 
mored cable, or single rubber covered wires in cir- 
cular loom are used; never use twin wire. When 



ELECTRICAL TABLES AND DATA 73 

one is alone on a fish job, a bell and battery con- 
nected to the fish wire with one pole, and to a coil 
of wire inserted in the hole at the other end with the 
other, is very useful. When the fish wire touches 
the other wire the bell will ring. Use a small chain 
for dropping and a spring wire for other work. 

Fixtures. — The height of hanging varies from 6 feet 
2 inches to 7 feet. The so-called art-domes are hung 
much lower, but they are a passing fad. 

Memorandum of Fixture Work 



Name 


Eoom or Circuit Number 


Address 






















































No. of gas lights 














^ Style of finish . 














£h Catalogue number 














T3 Sketch number 










































Size of holders 




























Height lowest point above floor 
Size of gas stub 








































No. of elec. lights 














Kind of sockets 














No. gas lights 














* Style of finish 




























a Sketch number 














(£} Kind of glassware 














Catalogue number 














Height above floor 














Size gas stub 




























No. switches 














Kind of switch 














Style of finish 





























74 



ELECTRICAL TABLES AND DATA 



The standard height of brackets is from 5£ to 6 
feet above floor. 

No fixture should ever be selected except with 
reference to the room in which it is to be hung, and 
it should be neither conspicuous for its expensiveness 
or cheapness. 

Elaborate fixtures made up of cheap material 
should never be used; pretense is always abomina- 
ble. Before installing, test each fixture for con- 
tinuity, short circuits and grounds ; move wires while 




Figure 6. — Method of Tying Knots in Flexible Cord. 



testing. The following memoranda will be of use in 
ordering fixtures: 

Flashers on branch circuits usually operate single 
pole. In such a case one-half of the cut-outs may be 
located at flasher, the other half, if more convenient, 
in the sign. Although the flasher allows the use of 
only a part of the lights at a time, it is customary to 
run mains for the full requirements of all the lights. 

Flat Irons constitute a considerable fire hazard and 
every precaution should be taken to install them 
safely. A pilot lamp is very useful. Provide extra 
flexible cord to help out the cord furnished with iron 
so the two will be long enough to allow iron to fall 
to the floor without straining fixture or other attach- 
ment. The common domestic flat irons weighing 



ELECTRICAL TABLES AND DATA 75 

from 3 to 8 lbs. require from 250 to 635 watts. A 
substantial metal stand should always be provided 
and should separate the iron about 2-J inches from 
cloth on board. 

Flexible Cord improperly used causes the majority 
of electrical fires. The common cord should always 
hang free in air ; should never be spliced, and should 
be soldered only where it connects to line wires. In 
sockets, rosettes, and outlet boxes it must be knotted 
to prevent strain from coming on the joints. The 
best method of tying knots is shown in Figure 6. 

Foundries. — The general illumination of foundries 
is commonly effected by means of arc lamps or clus- 
ters of incandescent lamps. The flaming arc is very 
effective. Strong shadows are useful, as all objects 
soon assume the same color. Cleaning of lamps is 
an important item and for this reason clusters of 
incandescent lamps are often encased in outer globes, 
which are more easily cleaned. In addition to the 
general illumination, each molder requires an indi- 
vidual lamp for his 'own use. 

Frequencies. — A frequency of 25 cycles per second 
is generally used for rotary converter work, and 
power transmission. Arc and incandescent lamps do 
not operate well with such low frequencies, hence a 
frequency of 60 cycles is generally used for illumina- 
tion. In any given circuit, the higher the frequency, 
the greater will be the reactance. If the frequency 
is too high for a given device the current will be 
insufficient, if too low it will be excessive. A fre- 
quency changer is a machine usually installed in 
substations. A frequency indicator is usually in- 
stalled upon switchboards, or used in connection 
with a large motor installation. 

Fuses. — Fuses are divided into three general 
classes: open, enclosed, and expulsion. The fuse 
metal itself is never hard enough to stand up well 



76 ELECTRICAL TABLES AND DATA 

under binding screws, hence copper tips are neces- 
sary. If these are not used there will be much un- 
necessary blowing 1 . All fuses should be placed in 
cabinets not only to prevent molten metal from caus- 
ing fires, but to insure greater reliability of the fuse 
by protecting it against drafts. The fusing of branch, 
and main circuits inside of buildings is thoroughly 
covered by the National Electrical Code. The rule in 
general is to provide fuse protection wherever the 
size of wire changes. The fuse to be of such size as 
to prevent current rise above the safe carrying ca- 
pacity of wires as given in the Code. Each motor or 
other translating device also requires separate fuse 
protection except that small devices aggregating not 
more than 660 watts capacity may be grouped under 
one fuse. 

All plans of fusing are a compromise between the 
desire to obtain adequate protection on the one hand, 
and escape the trouble caused by the many accidental 
breaks and uncalled for operations of fuses. 

Overhead systems as a rule are not fused where 
they leave the switchboard, but are equipped with 
switches or disconnectives. 

Feeders leaving the transmission lines are also 
usually left without fuse protection, but equipped 
with disconnectives. 

Fuse protection is fully demanded only where the 
chances of short circuits or grounds are quite great, 
and this point is not reached until the transformers 
are reached. It must be borne in mind that all con- 
sumers devices are protected by service fuses and 
switches, and these protect the outer lines fully 
against everything except what occurs on the poles. 
The primary side of transformers of small and me- 
dium capacity is usually protected by fuses, but the 
fuses are made large enough so that ordinary over- 
loads will not cause them to blow. 



ELECTRICAL TABLES AND DATA 77 

TABLE XXIII 

The following table gives fuse sizes often used 
with transformers of the capacities given. 

K.W. Capacity Size Fuse K.W. Capacity Size Fuse 

Amperes Amperes 
13 15 15 

2 3 20 15 

3 ' 3 25 20 

4 3 30 20 

5 5 40 30 
7Y 2 10 50 40 

10 10 

On the secondary side of transformers, fuses are 
not ordinarily used and it is not advisable to have 
them. In case a number of transformers feed a net- 
work the blowing of one fuse may cause the blowing 
of another, etc., until all are out. Under such cir- 
cumstances fuses cannot well be replaced until the 
load on the main is sufficiently reduced to allow one 
transformer to carry it, or until the feeder supplying 
the network has been opened ; in this case the feeder 
must be left open until all fuses have been replaced. 
In connection with underground circuits the case is 
different. Here short circuits and grounds are much 
more likely to occur. Such systems also always sup- 
ply a much larger number of customers within a 
given space, and more care is necessary. Under- 
ground networks are usually fused at each junction 
point so that, if an overload causes one fuse to blow, 
the other will follow and clear the balance of the 
circuits from trouble. Wherever parallel lines are 
run they should be equipped with reverse current 
circuit breakers. Three phase four wire systems are 
usually provided with a single pole switch in each 
leg, thus any phase can be disconnected without in- 
terfering seriously with the others. For three phase 
three wire systems three pole switches are used. All 
telephone circuits should be protected by fuse and 



78 ELECTRICAL TABLES AND DATA 

in addition with " sneak coils" and air gap arresters. 
Heat coils are arranged to open the circuit when a 
small or "sneak current " has passed through them 
for a considerable time, or a large current in an 
instant. Air gap arresters are supposed to open the 
circuit whenever unduly high potentials come to exist 
at their terminals. 







TABLE XXIV 










Tested Fuse 


Wire from y 2 to 


100 Amperes 




Safe 


Best Len 


g-ths for Use 








Carrying 


and Fusing- Cur- 


Length 


Mils. 


Capacity- 


rents 


for such 


Per Lb 




Diam 


Amperes 


Lengths 










Inches 


Amperes 


Ft. In 






% 


1 


11/2 


2550 




10 


% 


1 


2i/i 


1516 




13 


1 


IV 


3 


993 




16 


2 


1% 


5 


407 




25 


3 


1% 


7 


265 




31 


4 


1% 


9 


207 




35 


5 


1% 


10 


167 




39 


6 


2 


12 


144 




42 


7 


2 


13 


120 




46 


8 


2 


15 


.106 




49 


9 


2 


16 


94 




52 


10 


2% 


17 


84 




55 


12 


2% 


20 


68 




61 


14 


2% 


23 


58 




66 


15 


2% 


24 


55 




68 


16 


2i/ 2 


25 


49 




72 


18 


2y 2 


28 


43 




77 


20 


2y 2 


30 


37 


10 


82 


25 


2% 


37 


28 


9 


94 


30 


■2% 


43 


24 




103 


35 


3 


49 


20 




113 


40 


3 


56 


17 


2 


122 


45 


3 


62 


15 


4 


129 


50 


3 


69 


13 


6 


137 


60 


3% 


81 


10 


3 


158 


70 


3V4 ( 


93 


8 


10 


170 


75 


31/2 


99 


7 


9 


182 


80 - 


3% 


106 


7 


2 


189 


90 


31/2 


118 


5 


8 


212 


100 


4 


129 


5 







ELECTRICAL TABLES AND DATA 79 



Tested Fuse Strip from 50 to 600 Amperes 



Safe 


Best Lengths 


! for Use 


Weight 


Carrying 


and Fusing Cur- 


Per Foot 


Capacity 


rents for ; 


such 


Ounces 


Amperes 




Lengths 






Inches 




Amperes 




50 


3 




69 


1% 


60 


3% 




81 


1% 


70 


3% 




93 


1% 


75 


3V 2 




99 


1% 


80 


3y 2 , 




106 


2.% 


90 . 


3% 




118 


2y 2 


100 


4 




129 


3 


125 


4y 4 




158 


3% 


150 


1 4i/2 


— 


187 


4% 


175 


4% 




215 


6 


200 


4% 




243 


6% 


225 


4% 




270 


7% 


250 


4% 




298 


8% 


275 


4% 




325 


9% 


300 


5 




351 


10% 


350 


5% 




402 


12% 


400 


5%l 




450 


14% 


450 


5V 2 




500 


17 


500 


6 




550 


2oy 2 


600 


ey 2 




675 


35 



The current required to fuse metals can be found 
by the well known Preece formula: 

where I— current in amperes, d = diameter of wire, 
and a = a constant for different kinds of metal as given 
below : 



Copper 10244 Iron 3148 

Aluminum 7585 Lead 1379 

German Silver 5230 



80 



ELECTRICAL TABLES AND DATA 



The table below is calculated from the above for- 
mula and constants, and gives the current required 
to fuse wires of various sizes. 



TABLE XXV 



B. &S. 



Copper Aluminum German 
Silver 



Iron 



Lead 



4 


942 


698 


481 


290 


127 


6 


666 


493 


339 


204 


90 


8 


471 


349 


240 


145 


63 


10 


334 


247 


171 


103 


50 


12 


235 


174 


120 


72 


32 


14 


165 


122 


84 


51 


22 


16 


117 


86 


60 


35 


16 


18 


82 


60 


42 


25 


11 


20 


58 


43 


29 


18 


8 


21 


49 


36 


25 


15 


6 


22 


40 


29 


21 


12 


5 


23 


36 


26 


19 


11 


5 


24 


29 


21 


15 


9 


4 


25 


25 


18 


13 


8 


3 


26 


20 


15 


11 





3 


27 


17 


12 


9 


5 


2 


28 


14 


10 


7 


4 


2 


29 


12 


9 


6 


4 


1.5 


30 


10 


8 


5 


3 


1.2 


31 


8.5 


6 


4 


2.6 


1.0 


32 


7.0 


5 


4 


2.2 


0.9 



The strands of which flexible cord is made up 
range from No. 26 to 36. 

Galvanic. — A term much used in therapeutics to 
denote continuous, or direct current. 



ELECTRICAL TABLES AND DATA 81 

Garages. — The gasoline vapors so prevalent in 
garages do not ordinarily rise more than 4 feet above 
the floor. Avoid all possibility of electric sparks at 
this level, especially in pits. Electric lights should 
be well guarded with elastic lamp-guards which will 
protect the lamp against breakage even when it 
falls. 

Gas Lighting' may be effected by pilot flame, a 
small quantity of sponge platinum on mantle, or by 
high-tension electric sparks jumping a number of 
spark gaps in the gas jets, or low-tension sparks 
applied to jets in multiple. A spark coil is required 
and it should be connected with a tell-tale relay and 
bell which will ring in case the system becomes 
grounded. Electric gas lighting wires must not be 
used on same fixtures with electric light. 

Gauges. — The American, or Brown & Sharp wire 
gauge, abbreviated respectively A. W. G. or B. & S., 
is the one commonly used for measuring copper,, 
aluminum, and resistance wires in general. The 
U. S. steel wire gauge is commonly used for steel 
and iron wire. This is also known as the Washburn 
and Moen ; Koebling, and American Steel and Wire,, 
and is generally abbreviated Stl. W. G. 

The Birmingham or Stubs' Wire Gauge is some- 
times used for brass wire. It is commonly abbre- 
viated B. W. G. This, although spoken of as Stubs, 
is not identical with the Stubs' Steel Wire Gauge. 
The British Standard Wire Gauge, the Edison Wire 
Gauge and the Stubs ' Steel Wire Gauge are not much 
used in this country in electrical work. A compari- 
son of the different wire gauges is given below, 
diameters being given in mils (thousandths of an 
inch). 



ELECTRICAL TABLES AND DATA 



CIRCULAR OF THE BUREAU OF STANDARDS 









TABLE XXVI 








Tabular Comparison 


of Wire Gauges. 


Diameters in 


Mils. 


d 

© 
fcJO 


o3 c3 O 

4£s 


o 


£ © 
o3 bD 

bo os O 


h 05 

cc bX) 

II? 

•"£ .M 


i— i 05 

!.§ 

oa£ 


05 

- bJD 

,£3 ?-. eS 

£ 2 05 


d 

Q5 

bO 


7-0 




490.0 








500. 


7-0 


6-0 




461.5 








464. 


6-0 


5-0 




430.5 








432. 


5-0 


4-0 


460. 


393.8 


454. 


454. 




400. 


4-0 


3-0 


410. 


362.5 


425. 


425. 




372. 


3-0 


2-0 


365. 


331.0 


380. 


380. 




348. 


2-0 





325. 


300.5 


340. 


340. 




324. 





1 


289. 


283.0 


300. 


300. 


227. 


300. 


1 


2 


258. 


262.5 


284. 


284. 


219. 


276. 


2 


3 


229. 


243.7 


259. 


259. 


212. 


252. 


3 


4 


204. 


225.3 


233. 


238. 


207. 


232. 


4 


.5 


182. 


207.0 


220. 


220. 


204. 


212. 


5 


6 


162. 


192.0 


203. 


203. 


201. 


192. 


6 


7 


144. 


177.0 


180. 


180. 


199. 


176. 


7 


8 


128. 


162.0 


165. 


165. 


197. 


160. 


'8 


9 


114. 


148.3 


148. 


148. 


194. 


144. 


9 


10 


102. 


135.0 


134. 


134. 


191. 


128. 


10 


11 


91. 


120.5 


120. 


120. 


1S8. 


116. 


11 


12 


81. 


105.5 


109. 


109. 


185. 


104. 


12 


13 


72. 


91.5 


95. 


95. 


182. 


92. 


13 


14 


64. 


80.0 


83. 


83. 


ISO. 


80. 


14 


15 


57. 


72.0 


72 


72. 


178. 


72. 


15 


16 


51. 


62.5 


65. 


65. 


175. 


64. 


16 


17 


45. 


54.0 


58. 


58. 


172. 


56. 


17 


18 


40. 


47.5 


49. 


49. 


168. 


48. 


18 


19 


36. 


41.0 


42. 


40. 


164. 


40. 


19 


20 


32. 


34.8 


35. 


35. 


161. 


36. 


20 


.21 


28.5 


31.7 


32. 


31.5 


157. 


32. 


21 


22 


25.3 


28.6 


28. 


29.5 


155. 


28. 


22 



ELECTRICAL TABLES AND DATA 



© 

© 

bjo 

Pi 

o 


American 
Wire Gauge 
(B. & S.) 22 


CD r-< 


Birmingham 
Wire Gauge 
(Stubs') 


Old English 

Wire Gauge 
(London) 


U 1 © 
OJ fejo 

I.S 


(British) 
Standard 
Wire Gauge 


d 

CD 

bn 



O 


23 


22.6 


25.8 


25. 


27.0 


153. 


24. 


23 


24 


2CL1 


23.0 


22. 


25.0 


151. 


22. 


24 


25 


17.9 


20.4 


20. 


23.0 


148. 


20. 


25 


26 


15.9 


18.1 


18. 


20.5 


146. 


18. 


26 


27 


14.2 


17.3 


16. 


18.75 


143. 


16.4 


27 


28 


12.6 


16.2 


14. 


16.50 


139. 


14.8 


28 


29 


11.3 


15.0 


13. 


15.50 


134. - 


13.6 


29 


30 


10,0 


14.0 


12. 


13.75 


127. 


12.4 


30 


31 


8.9 


13.2 


10. 


12.25 


120. 


11.6 


31 


32 


8.0 


12.8 


9. 


11.25 


115. 


10.8 


32. 


33 


7.1 


11.8 


8. 


10.25 


112. 


10.0 


33 


34 


6.3 


10.4 


7. 


9.50 


110. 


9.2 


34 


35 


56 


9.5 


5. 


9.00 


108. 


8.4 


35 


36 


5.0 


9.0 


4. 


7.50 


106. 


7.6 


36 


37 


4.5 


8.5 




6.50 


103. 


6.8 


37 


38 


4.0 


8.0 




5.75 


101. 


6.0 


38 


39 


3.5 


7.5 




5.00 


99. 


5.2 


39 


40 


3.1 


7.0 




4.50 


97. 


4.8 


40 


41 




6.6 






95. 


4.4 


41 


42 




6.2 






92. 


4.0 


42. 


43 




6.0 






88. 


3.6 


43 


44 




5.8 






85. 


3.2 


44 


45 




5.5 






81. 


2.8 


45 


46 




5.2 






79. 


2.4 


46 


47 




5.0 






77. 


2.0 


47 


48 




4.8 






75. 


1.6 


48 


49 




4.6 






72. 


1.2 


49 


50 




4.4 






69. 


1.0 


50 



The American Wire Gauge sizes have here been rounded off 
to about the usual limits of commercial accuracy. 

The Steel Wfrre Gauge is the same gauge which has been 
known by the various names: li Washburn and Moen, " 
"Boebling," " American Steel and Ware Co. 's." Its abbre- 
viation should be written ' ' Stl. W. G ., ' ' to distinguish it front 
"S. W. G., " the usual abbreviation for the (British) Stand- 
ard Wire Gauge. 



84 ELECTRICAL TABLES AND DATA 

Generators. — Alternating Current generators may 
be of the revolving field or revolving armature type. 
The revolving field type is easier to insulate and less 
troublesome to maintain, hence is most widely used. 
There is another, known as an inductor type, in which 
usually all electrical parts are stationery and an iron 
spider is caused to revolve, it being so arranged as 
alternately and regularly to alter the magnetic flux 
and thus cause induction of e. m. f . This type is not 
much used. 

The so-called Induction generator is another type, 
and is similar to an induction motor; in fact, an 
induction motor, when driven above the speed of 
synchronism becomes an induction generator, and 
delivers current to the line. This type of generator 
cannot operate unless other alternators provide it 
with the necessary exciting current. The capacity in 
generators for field excitation must be nearly equal 
to one-third of the capacity of the induction gener- 
ators. This type of generator is well suited for fluc- 
tuating speeds such as are given by gas engines, but 
it can never constitute an entire plant. Alternating 
current generators are made to operate single-phase, 
two-phase and three-phase. The single-phase machine 
is not well suited for power work, and is more expen- 
sive per unit of output than polyphase machines. 
The two-phase generators are, as a rule, used only 
on old direct current installations which have been 
adapted to a.-c. operation. The three-phase system 
is the most economical and is almost universally used. 
It is well suited for either light or power transmission. 
Alternators may be built to be self -exciting, bui this 
is not often done. Most of them require a direct 
current exciter. 

Efficiency. — Approximate efficiencies of generators 
of various sizes are given about as follows: 100 
K.V.A., 91 per cent; 500, 94; 1,000, 95; 2,000, 96; 



ELECTRICAL TABLES AND DATA 85 

3,000, 96 to 97 ; 5,000, 97 or better. These efficiencies 
vary of course with the power factor, load, voltage, 
etc. 

Frequency. — The common frequencies are 25 and 
60 cycles per second, the lower being used for trans- 
mission to substations and for power alone. The 
higher frequency is used for mixed lighting and 
power, and also for lighting alone. In a single-phase 
machine the current and voltage per phase have but 
one meaning. The power is equal to Zx^xpower 
factor, and the product of volts and amperes gives 
the volt-ampere rating of the machine. In a two- 
phase alternator each half supplies half of the cur- 
rent and power. The usual four transmission wires 
are sometimes combined into three wires, and in such 
a case the voltage between the two outside wires is 
1.41 times the phase voltage, and the current in the 
middle wire is 1.41 times the current in the outside 
wires. The power in such a combination may be 
found in two ways. Measuring current in the middle 
wire and the voltage across both phases, the power is 
equal to IxE x power factor. Measuring current in 
one of the outside wires, and using phase voltage, the 
power is equal to / x 2? x 2 x power factor. Three- 
phase generators are always connected by means of 
3 main wires, and sometimes a neutral, but may be 
either delta or star. If the delta connection is used, 
the phase voltage is the same as the voltage between 
any two wires, but the current in any phase is 1.73 
times the current in any one of the wires. If the star 
connection is used, the voltage between any two wires 
is 1.73 times the voltage of any phase winding, and 
the current to deliver the same power will be only 
0.58 of the former current in the line wires. The 
power with either connection is equal to 7x2£xl.73x 
power factor* 

Frequencies. — The common frequencies are 60 and 



86 ELECTRICAL TABLES AND DATA 

25 cycles. The higher frequency is used for light, 
and mixed light and power loads. The lower is used 
for power alone and also for transmission lines to 
substations or converters. The frequency of any gen- 
erator depends upon the speed and number of poles 
and may be found by the formula: 

._ r. p.m. number of poles 
'" 60 X 2 

The table below shows the speeds at which gener- 
ators provided with a certain number of poles must 
operate to deliver current at the frequencies given. 





TABLE XXVII 












60 Cycles. 








No. Poles. . . . 


.... 4 


8 12 


16 


20 


24 


R. P. M 


....1,800 


900 600 
25 Cycles. 


450 


360 


300 


No. Poles.... 


.... 4 


8 12 


16 


20 


24 


E. P. M 


.... 750 


375 250 


187i/ 2 


150 


125 



Operation of Alternators in Parallel. — In order 
that alternators may be operated in parallel they 
must be identical in four respects. The frequency 
must be the same. The voltage must be the same. 
The current and voltages must be in phase, i.e., their 
maxima and minima must occur at the same instant. 
The wave form of the machines should be as near as 
possible alike. 

The frequency is governed by the speed, and. if it 
is not correct, the speed must be adjusted either by 



ELECTRICAL TABLES AND DATA 87 

adjusting the engine, or diameters of pulleys. The 
voltage can be determined by a voltmeter test. 

Whether the machines are in or out of phase can 
be determined only by properly connected synchroniz- 
ing lamps, or synchronizing instruments. 

The synchronizing and keeping in step of alter- 
nators will be made easier by synchronizing the piston 
strokes of engines as far as possible if they are sepa- 
rately driven, or, if driven from a common shaft, by 
running one of the machines with a slack belt, which 
will allow it to fall in step more readily. "Where 
synchroscopes are used the pointer will indicate which 
machine is running too fast or too slow: Where the 
synchronizing is done with lamps they may be con- 
nected so as to indicate synchronism either by dark- 
ness or light. If the machines are not in phase there 
will be alternations of darkness and light in the lamps 
which will alternate with great rapidity if the ma- 
chines are much out of synchronism, but will be at 
longer and longer intervals as they are brought more 
nearly into step. The proper time to close the switch 
is just a moment before the period of full darkness. 
If the machines are nearly in synchronism when 
thrown together, there will be cross current which 
will help to bring them together, but it is best to 
have them synchronized perfectly before connecting. 

The load cannot be divided among alternators by 
increasing the field excitation as with direct-current 
machines; it is necessary to give more steam to the 
engine of the light running generator. This tends to 
advance the generator and causes it to take more cur- 
rent. The power factor can be improved or altered 
by adjusting the field excitation. Adjust fields so 
that power factor of each machine is the same. 

Single Machine, Operation of. — See that machine 
is entirely disconnected from the load. Inspect all 
bearings and see that they are well oiled and that oil 



88 ELECTRICAL TABLES AND DATA 

rings work properly. Adjust field rheostat so that 
all resistence is in circuit and close exciter circuit. 
Start machine, bringing it gradually up to speed and 
cutting out resistance in field rheostat until generator 
voltage comes to its proper value. Next throw in 
switches, bringing load on gradually if possible, and 
adjust rheostat to maintain voltage properly. Test 
speed to see that it is at its proper value ; the speed 
is of greater importance with alternators than with 
direct current generators. 

Rating. — For full details as to rating, the reader 
is referred to the Standardization Eules of the 
A. I. E. E., which are too lengthy to be given 
here. 

The maximum, or continuous, rating of an alter- 
nator is commonly taken as the load in kilowatts it 
can carry at 100 per cent power factor with a maxi- 
mum rise in temperature of any part of 50° C. 
(122° F.) above the surrounding air when that is 
25° C. (77° F). Corrections for other surrounding 
temperatures to be made according to A. I. E. E. 
Standardization Rules. Another rating, used mostly 
in connection with street railway work, allows a tem- 
perature rise of 45° C. (113° F.) under the same 
conditions as above, and requires that 50 per cent 
more than the rated load used for two hours shall not 
cause a temperature rise of more than 55° C. 
(131° F.). 

Voltage. — A voltage in excess of 12,000 or 13,000 is 
rarely generated direct; higher line voltages are ob- 
tained mostly by step-up transformers. 

Direct Current Generators, Compound Machines. — 
This is a combination of shunt and series dynamo, 
and a distinct improvement over the shunt machine. 
The compound winding can be adjusted to regulate 
the voltage as desired. It requires the same instru- 
ments as the shunt, and in addition heavy equalizing 



ELECTRICAL TABLES AND DATA 89 

wires run between each pair of machines. These 
should be carried to the board and the main switch 
should be triple pole. The machine may be connected 
either long shunt (shunt winding bridging compound 
fields as well as armature), or short shunt (shunt 
field bridging only armature) ; it is merely a ques- 
tion of convenience. All these machines may be 
bi-polar or multi-polar, direct or belt connected and 
provided with com mutating or interpoles. 

Bating. — Machines are commonly rated on the 
basis of their continuous output in kilowatts with a 
maximum rise in temperature of 50° C. (122° F.) 
above the surrounding air at 25° C. (77° F.). For 
full information see A. I. E. E. Standardization 
Rules. The common voltages are 110 volts for light- 
ing and small power (used mostly in isolated plants) ; 
220 to 250 also for lighting and power, but used 
mostly in larger plants, and for short distance dis- 
tribution; 500 to 600 volts, used almost exclusively 
for street railway work ; 2,000 to 6,000, or more, used 
for series arc lighting by direct current. 

The Series Machine is used only for constant cur- 
rent work. It requires the following instruments and 
fittings : 

Short circuiting switch for fields. 

Ammeter, a switchboard equipped with plugs and 
jacks. 

A polarity indicator is often advisable. 

The Shunt Machine is used for all variable current 
work. Its voltage regulation is poor, and requires 
constant attention. It requires a field rheostat, fuses, 
main switch or circuit breaker, volt meter, ammeter, 
ground detector, switchboard and pilot lamps. The 
voltage of this machine is variable and automatically 
decreases with an increase in the devices it supplies. 

Greek Alphabet. — Greek letters have become the 
standard symbols for many quantities dealt with in 



$0 ELECTRICAL TABLES AND DATA 

electrical and mechanical calculations. The letters 
and their pronunciations are given below: 

A a — Alpha. I i — Iota. P p — Rho. 

B (3 — Beta. K k — Kappa. 5 o- — Sigma. 

r y — Gamma. A X — Lambda. T r — Tau. 

A 8 — Delta. M /x — Mu. Y v — Upsilon. 

E e — Epsilon. N v — Nu. 3> <f> — Phi. 

Z £ — Zeta. S £ — Xi. X x — Chi. 

H rj — Eta. O o- — Omicron. * \j/ — Psi. 

© — Theta. n tt — Pi. O w — Omega. 

Gram or Gramme. — The gramme is the mass of a 
cubic centimeter of water at the temperature of its 
greatest density. It is the unit of mass and is equal 
to 15.43235 grains; 7,000 grains equal 1 lb. av. 

Gravity Cell. — This is a cell in which copper and 
zinc immersed in a solution of blue vitriol are the 
active elements. It is used for continuous work and 
where small constant currents only are required. 

Ground Detectors. — It is customary to provide 
ground detectors on all switchboards from which 
entirely insulated circuits are run. Tests should be 
made quite frequently, so as to catch a ground as soon 
as it comes on. When grounds exist on both sides of 
a system, detectors are not reliable and the part to 
be tested must be disconnected from the board. Con- 
tinuously indicating detectors are preferable; static 
instruments are made which can be so used even on 
high voltage lines with perfect safety. 

Grounding. — Any connection of any part of a cur- 
rent carrying conductor, or live metal part of any 
device which has become connected to a foreign con- 
ducting medium so as to deliver current or potential 
to it, is spoken of as being grounded. Some devices 
and circuits are purposely grounded, the frame or 
the earth being relied upon as return conductors. 



ELECTRICAL TABLES AND DATA 91 

The purposive grounding 1 of wires used in connection 
with, electrical work may be divided into two classes: 
The grounding of frames, conduits, etc., which are 
not supposed to become alive except through a break- 
down of the insulation, and the grounding of wires, 
or devices which usually do carry current. The life 
and fire hazard from electrical sources may be greatly 
reduced by improving the insulation, so that the 
chance of any person or material being affected by the 
current is small, or by arranging a bypath which 
shall carry the current safely away in case live parts 
of the conductors come in contact with it. To provide 
such a shunt is the object of all grounding. 

Wherever a ground connection is provided, it in- 
creases the liability of a breakdown in the insulation 
of the device, but at the same time reduces the possi- 
bility of serious damage from that source. Connect- 
ing the frame of any device to ground weakens the 
natural insulation of that device, but protects persons 
and property otherwise liable to injury to a consider- 
able extent. Good cause for the grounding of live 
parts of electrical circuits for the purpose of protec- 
tion exists only in cases where two or more voltages 
exist in such close proximity that there is liability of 
the higher voltage becoming impressed upon parts 
normally intended only for the lower voltage. And 
even under these conditions the N. E. C. authorizes 
the grounding only when, normally, no current is 
supposed to be flowing over the ground connections. 
The grounding of any part of a live circuit under the 
above conditions increases the chances of trouble but 
confines the trouble to that which may be possible 
with the lower voltage. If, for instance, the ground 
on the secondary of a transformer is in perfect con- 
dition, it will give positive assurance that the primary 
voltage cannot be impressed upon any part of the 
secondary system, but it will also give assurance that 



92 ELECTRICAL TABLES AND DATA 

any workman who may come in contact with live 
parts on the ungrounded side, while making a ground 
himself, will receive the full benefit of the secondary 
voltage. In general, since the grounding takes away 
the natural insulation, which is often relied upon to 
some extent but quite often does not exist at all, it 
will force upon manufacturers a higher standard of 
construction, and the net result will be increased 
safety in all respects except life. In order to keep 
the life hazard within bounds it is not customary to 
ground live wires operating with a potential above 
250. 

As a general rule, all metallic structures or pipes 
not normally connected to electrical sources, but 
liable to be accidentally so connected, should be 
grounded. Connection to an extensive water pipe 
system makes the best possible ground. Steam and 
hot water piping is not so reliable even if connected 
to water pipe systems. The steel frames of buildings 
are useful only with supposedly smell currents con- 
fined to the same building. Gas piping is likely to 
cause fires if contacts work loose, or if there is any 
electrolytic action. "Where the above means of making 
ground connections are not available the most eco- 
nomical connection is made with a galvanized iron 
pipe driven into the ground. The practice of one 
large company is to use a 1-J-inch pipe 8 feet long, 
and drive its full length into the ground, burying the 
connection with it. Another company uses a -J- or 
f-inch pipe. The resistance of the ground itself is 
so much higher than that of the pipe that the con- 
ductivity of the larger pipe is not much better than 
that of the smaller, but it is more reliable for driving 
purposes. "Where the ground is of very great impor- 
tance, it is advisable to use several pipes. The pipe 
should enter the earth at least 6 feet, and it is prob- 
able that an additional foot or two will more than 



ELECTRICAL. TABLES AND DATA 93 

double the usefulness in dry seasons. The resistance 
of the earth varies with its composition, its degree of 
moisture, and distance from piping, etc. Gravel and 
sa^id, because so easily drained, make very poor 
grounds, and rock cannot be used at all. 

Overhead cables and messenger wires are provided 
with about one ground per mile. Ground connections 
may be tested with an ammeter and a voltmeter. 

Connect one pole of current source to nearest hy- 
drant or other available piping and the other to the 
ground. The voltage divided by the current will 
equal the resistance of the ground, since the piping 
itself may be considered as comparatively without 
resistance. 

Hanger Boards are required for incandescent 
lamps indoors on series circuits, but are not neces- 
sary with arc lamps, although advisable. 

Heat Coils are usually installed in connection with 
signaling circuits. They are arranged to open the 
circuit when a large current flows through them for 
a short time or a small current for a longer time. 
Their office is to guard against sneak currents too 
small to blow fuses. 

Heating by Electricity. — The heating of buildings 
by electricity is not commercially practicable, except 
on a small scale, or under particularly favorable cir- 
sumstances. It is used on a large scale only in con- 
nection with street cars. In residences, offices, fac- 
tories, etc., it is used only for small spaces, or where 
a limited quantity of heat is required for a short 
time only. Since there is practically no heat wasted, 
no air vitiated, little space occupied, no dirt caused, 
the fire hazard greatly reduced and the heaters are 
easily portable, it compares under suitable conditions, 
very favorably with other means of heating. One 
watt hour will raise the temperature of 1 cubic foot 
of air about 200 degrees Fahrenheit. 



94 ELECTRICAL TABLES AND DATA 

The heat represented by one B. T. U. is sufficient to 
raise the temperature of 1 lb. of water or 55 cubic 
feet of air 1 degree Fahrenheit. One watt equals 
3.412 B. T. U.S. 

In order to heat a room properly we must first 
supply sufficient heat to raise the temperature the 
required amount; next, furnish a steady supply of 
heat to make up for the absorption of walls, floor and 
ceiling; third, heat the fresh air which must be ad- 
mitted for ventilating purposes. For a rough esti- 
mate it is customary to require from one to two 
watts per cu. ft. in room. 

The wattage necessary to raise the temperature of 
a room may, however, be more accurately found by 
the formula: 

Cxi 60 
200 m 
where W = watts 

= cubic feet of air in room 
t = number of degrees F. that temperature 

must be raised 
m = the number of minutes in which this rise 
must take place. 

The above formula makes no allowance for radiation 
or ventilation. 

Under average conditions it may be assumed that 
every square foot of wall, ceiling, and floor space will 
absorb heat as given in Table XXX for various tem- 
peratures. If we multiply the surfaces by the num- 
bers given we shall obtain the rate at which watts 
must be supplied to maintain the temperature in a 
hermetically sealed room after the desired tempera- 
ture has been secured. 

Every human being should be provided with 3,000 
cubic feet of fresh air per hour, although it is possible 



ELECTRICAL TABLES AND DATA 95 

to do comfortably with 2,000 feet. If the allowance 
per hour, however, is as low as 1,000 feet, conditions 
will be decidedly injurious to health and also imme- 
diately uncomfortable. Since all rooms electrically 
heated are small, fresh air requirements demand that 
the air must be changed several times per hour. In 
order to facilitate the calculations three tables are 
provided. Table XXVIII shows the number of cubic 
feet of air contained in rooms of various dimensions 
likely to be warmed with electrical heat, the height of 
rooms being assumed as 9 feet. This table also shows 
the number of square feet of radiating surface, includ- 
ing ceiling and floor. There is further given, in 
connection with each size of room, the number of times 
the air should be changed per hour for each occupant 
to afford fair ventilation. The figures given are such 
as it is believed the occupants will naturally provide 
by opening windows or doors. 

In Table XXIX we have constants by which the. 
cubic contents of rooms must be multiplied to find 
the number of watts necessary to raise the tempera- 
ture of rooms the number of degrees given at top, in 
the number of minutes given at the left. To find the 
watts necessary to provide for air changes per hour 
we must multiply the cubic contents by the constants 
given for 60 minutes and by the number of times per 
hour the air is to be changed. 

To find the watts lost in radiation we multiply the 
wall surface by the figures given in Table~ XXX. 

Example. — A bathroom 6 by 8 feet is to be heated 
20 degrees F. above the temperature of the surround- 
ing rooms and the rise in temperature must be brought 
about in five minutes and then maintained for an 
hour afterward. "What size of heater will be required ? 
There are 432 cu. ft. in such a room and by Table 
XXIX for 20 degrees and five minutes we find 1.20 
and multiplying this by 432 we have 518 watts re- 



96 ELECTRICAL TABLES AND DATA 

quired to heat the air without allowing for conduction 
or ventilation. From Table XXVIII we also see 
tliat there are 348 feet of surface which, multiplied 
by 2.5, taken from Table XXX, for twenty degrees, 
give us 870 watts to make up for conduction through 
walls. Table XXVIII further shows that the air 
ought to be changed five times per hour; hence, tak- 
ing the constant 0.10 from Table XXIX for 60 min- 
utes and 20 degrees and multiplying this by 5, we 
have 0.50, and this, multiplied by the number of 
cu. ft., gives us 216 watts for air changes, and this, 
added to 870 watts for conduction, gives us a total 
of 1,088 watts to keep up the temperature of four 
bathroom 20 degrees above that of the surrounding 
rooms. A 1,500-watt heater would serve such a room 
very nicely. 

Every occupant of such a room will contribute 
about 125 watts of this. 

With all doors and windows closed the average 
house is supposed to allow a change of air at least 
once per hour. 

If a room is to be used only for a short time, a 
change of once per hour may thus be calculated upon. 
In laying out heating plants in residences where com- ' 
fort of the user is the main desideratum, it is advis- 
able to err on the side of plentiful capacity; in com- 
mercial installations where the installation is more 
for the benefit of workmen it may be more judicious 
to err in the interest of a somewhat small capacity. 

In small rooms a heater should always be placed 
as near as possible where the cold air enters, but in 
large rooms, if only a portion of the room is to be 
heated, it should be located out of the way of drafts. 
The coils should be divided into proportional sections 
equal to 1 and 2. This will enable l/3d, 2/3ds or 
the full capacity of the heater to be used as desired. 
Electric heating has one advantage over other forms. 



ELECTRICAL TABLES AND DATA 97 

and this consists in its ability to give instantaneous 
results, and these are best attained with heaters of 
comparatively large capacity, so that there will be no 
temptation to keep up the temperature except when 
it is actually needed. 

TABLE XXVILT 

Showing number of cu. ft.; wall surfaces (includ- 
ing ceiling and floor) and necessary changes of air per 
occupant per hour in room of dimensions given ; height 
of ceiling 9 ft. 

Width Length in Feet. 

5 6 7 8 9 10 11 12 

fCu. feet 225 270 315 360 405 450 495 540 

5 J Wall surf ace.. 230 258 286 314 342 370 398 426 
[Air changes.. 9 8 .7 6 5 54 4 

("Cu. feet 270 324 378 432 486 540 594 648 

6 \ Wall surf ace.. 258 288 318 348 378 408 438 468 
[Air changes.. 866 5 4443 
fCu. feet 315 378 441 504 567 630 693 756 

7 \ Wall surf ace.. 286 318 350 382 414 446 478 510 
[Air changes.. 76544333 

fCu. feet 360 432 504 576 648 720 792 864 

8 \ Wall surf ace.. 314 348 382 416 450 484 518 552 
[Air "changes.. 65443333 

fCu. feet 405 486 567 648 729 810 891 972 

9 \ Wall surf ace.. 342 378 414 450 486 522 558 594 
[Air changes.. 5 4 4 3 3 2.5 2.2 2 

fCu. feet 450 540 630 720 810 900 9901,080 

10 J Wall surf ace.. 370 408 446 484 522 560 598 636 
[Air changes.. 4.4 4 3.2 3 -2.5 2.3 2 2 

[Cu. feet 495 594 693 792 891 9901,0891,188 

11 \ Wall surf ace.. 398 438 478 518 558 598 638 678 
[Air changes.. 4 3.2 3 2.6 2.2 2.0 1.9 1.7 

fCu. feet 540 648 756 864 9721,080 1,188 1,296 

12 { Wall surf ace.. 426 468 510 552 594 636 678 720 
[Air changes.. 4 3 2.6 2.3 2 2 1.8 1.7 



98 ELECTRICAL TABLES AND DATA 

TABLE XXIX 

To find watts required to heat air in room (no 
allowance for radiation or changes) multiply cubic 
feet of air by factor in table below. 

Minutes in which Bise in Temperature, I\ 

rise is to take place 10 15 20 25 30 35 40 

5 0.60 0.90 1.20 1.50 1.80 2.10 2.40 

10 0.30 0.45 0.60 0.75 0.90 1.05 1.20 

15 0.20 0.30 0.40 0.50 0.60 0.70 0.80 

SO 0.10 0.15 0.20 0.25 0.30 0.35 0.40 

45 0.07 0.10 0.14 0.17 0.20 0.23 0.27 

60 0.05 0.07 0.10 0.12 0.15 0.18 0.20 



TABLE XXX 

To find watts needed to make up for conduction 
multiply wall surface by factors below. 







Temperature Bise 






10 

1.5 


15 

2.0 


20 25 30 
2.5 3.1 3.6 


35 
4.3 


40 

5.0 



To find watts necessary for ventilation, multiply 
watts required to heat air in 60 minutes by number 
of changes of air required per hour. 

DOMESTIC HEATING DEVICES 
(77estinghouse Electric & Mfg. Co.) 

Apparatus Watts 

Broilers, 3 ht 300 to 1,200 

Chafing dishes, 3 ht. 200 to 500 

Cigar lighters 75 

Coffee percolators 380 

Coil heaters 110 to 440 

Corn poppers 300 

Curling irons 15 

Curling iron heaters 60 



ELECTRICAL TABLES AND DATA 99 

Apparatus Watts 

Double boilers for 6 in. 3 ht. stove 100 to 440 

Flat irons, 3 to 8 lbs., domestic sizes 250 to 635 

Foot warmers 50 to 400 

Frying kettle, 8 in 825 

Frying ^pan 250 to 500 

Griddle cake cookers, 9x12, 3 ht 330 to 880 

Griddle cake cookers, 12x18, 3 kt 500 to 1,500 

Grill 600 

Heating pads 50 

Instantaneous flow water heaters 2,000 

Kitchenettes (complete), average 1,500 

Nursery milk warmers 500 

Ornamental stoves 250 to 500 

Ovens 1,200 to 1,500 

Plate warmers 300 

Radiators . 500 to 6,000 

Eanges, three heats, 4 to 6 people 1,000 to 4,515 

Ranges, three heats, 6 to 12 people 1,100 to 5,250 

Ranges, three heats, 12 to 20 people 2,000 to 7,200 

Samovar . . 500 

Saute pans 165 to 660 

Shaving mugs 150 

Stoves (plain) 4 in 50 to 220 

Stoves (plain) 6 in., 3 ht 125 to 500 

Stoves (plain) 7 in., 3 ht 120 to 600 

Stoves (plain) 8 in., 3 ht 165 to 825 

Stoves (plain) 10 in., 3 ht 275 to 1,100 

Stoves (plain) 12 in., 3 ht 325 to 1,300 

Stoves, traveler's . . . . 200 

Toaster stoves, 5 in. by 9 in .- 500 

Toasters, 9 in. by 12 in., 3 ht... 330 to 880 

Toasters, 12 in. by 18 in., 3 ht 500 to 1,500 

Urns, 1 gal., 3 ht 110 to 440 

Urns, 3 gal., 3 ht 220 to 440 

Urns, 3 gal., 3 ht 330 to 1,320 

Urns, 5 gal., 3 ht 400 to 1,700 

Waffle irons, two waffles 770 

Waffle irons, three waffles 1,150 

Water cup 500 

Water heater, bayonet type 700 to 1,500 



ELECTRICAL TABLES AND DATA 



ELECTRIC HEATING DEVICES FOR INDUSTRIAL PURPOSES 

Apparatus Watts 

Annealing furnaces 200 

Bar or barbers' urns, 1 to 5 gal., 3 ht 200 to 1,700 

Bakers ' ovens, 30 to 80 loaves 6,000 to 10,000 

Branding tool 10 to 500 

Button dye heater 100 

Chocolate warmers 55 to 250 

Coffee urns, 1 to 20 gal 200 to 4,000 

Corset irons 350 

Dental furnaces 450 

Embossing head 100 to 1,000 

Glue pot, % pt. to 25 gal 150 to 5,000 

Glue pots 110 to S80 

Hat irons (small) 200 

Hatters' iron, 9 to 15 pounds 450 

Instrument sterilizers 350 to 500 

Japanning oven 1,000 to 10,000 

Laboratory apparatus flask heaters 500 

Linotype pots 485 

Machine irons, 2 to 18 lbs 770 

Matrix dryer 28,000 

Melting pot 13,000 to 30,000 

Oil tempering bath . . 6,000 to 20,000 

Pitch kettles, 12 and 15 in. 3 ht 300 to 1,500 

Polishing irons, 3.5 to 5.5 lbs 330 to 550 

Eadiators, various sizes 700 to 6,000 

Sealing wax pots, .5 to 1.5 pt 175 to 300 

Shoe irons .200 

Soldering irons (various sizes) 100 to 450 

Soldering pots, 4 to 15 lbs. capacity 200 to 440 

Tailors ' iron, 12 to 25 lbs 660 to 880 

Vulcanizers for automobile tires 100 to 450 



ELECTRICAL TABLES AND DATA 101 

High Tension. — The N.E. C. classifies as "high 
potential" all voltages above 550 and below 3500, 
allowing a 10 per- cent additional in the case of 550 
volt motors. Voltages above 3500 are classed as ' 
"extra high potential." Special points to be noted 
with very high potentials are the Corona effect and 
the fact that ordinary bushings must not be used 
where wires enter buildings. It is best to enter wires 
through large open spaces. 

Horsepower. — 746 watts equal 1 horsepower, 
abbreviated H. P. One H. P. is sufficient to raise 
33,000 lbs. 1 foot per minute or 1 lb. 33,000 feet per 
minute. 

Hospitals. — In the corridors, only an indifferent 
illumination of about 0.5 watts per square foot is 
needed. Good exit and emergency lighting is usually 
insisted upon and as most of the inmates are helpless 
every possible precaution against the fire hazard 
should be taken. Good ventilation is also essential. 

In the public wards inverted lighting or lights 
encased in strongly diffusing globes would give the 
best results. By no means should direct lighting 
from the ceiling be favored. A plentiful supply of 
outlets for heating pads, etc., will be found convenient. 

In the private wards the illumination should be by 
means of lights placed at the head of bed and never 
by ceiling lights. Each lamp should be controllable 
by pendant switch, so as to enable patient to operate 
it. Separate receptacle for heating pads and other 
devices should be provided. In the operating rooms a 
very bright shadowless illumination should be pro- 
vided, and this should be fitted with ample switching 
facilities so as to adjust it to the special needs of any 
operating physician. Arrange the operating lights so 
that no one fuse can put all of them out, or at least 
provide throw over switch to another set of fuses. 
Signaling circuits are usually also provided for all 
patients. 



102 ELECTRICAL TABLES AND DATA 

Hotels. — Exit and emergency lights should be pro- 
vided in all large hotels. It is a good plan to arrange 
the lighting so that two circuits enter each room or 
apartment which contains more than one outlet. 
Where floors are alike this can sometimes be done by 
running branch circuits straight up and down, and 
locating all cut-outs in basement. Hall circuits should 
always be independent of room circuits, so as to reas- 
sure guests in case of a blowout of large fuse, or other 
accident which darkens a large part of the house. 
Door switches will be found useful for closets as well 
as for rooms. Vacuum cleaner circuits should be pro- 
vided in all halls, close enough together to avoid the 
use of very long cords. In the case of hotels planned 
for families, a large number of outlets with which to 
supply lights for illumination of pictures, lamps in 
cozy corners, etc., will be useful. If these are not pro- 
vided, the rooms will likely soon be found strung full 
of flexible cord, which will introduce a considerable 
fire risk. Special systems of wiring enabling one to 
turn on lights in rooms even though* they be switched 
off there, will be very serviceable in case of fire or 
panic, but will add considerable to the expense. In 
large hotels equipped with banquet halls, carriage 
calls are often provided. In such halls a special outlet 
for moving picture arc, or stereopticon should be 
provided. 

Hunting. — Whenever anything causes fluctuations 
in the speed of an alternator operating in parallel with 
others, it will either deliver current to the others or 
draw current from them. Under certain circumstances 
this condition may become fixed and the machines are 
then said to be hunting or phase swinging. This 
condition is liable to be most severe with machines 
having a large number of poles. To prevent hunting 
the prime mover should have a governor which is not 
too sensitive. The connections between the machines 



ELECTRICAL TABLES AND DATA 103 

should not have too much resistance, and the ma- 
chines should be equipped -with damping coils. To 
prevent excessive short circuits, reactances are some- 
times cut into the external circuit. To prevent over- 
heating, thermometers or pyrometers electrically con- 
nected are sometimes embedded in the hottest parts 
of machines and arranged to indicate temperatures 
at the outside. 

Hysterisis. — This is the term which describes the 
lagging of the magnetism behind the magnetizing 
force. It causes heating of the iron and loss of 
energy, and is much greater with steel than with soft 
iron. 

Illumination. — Illuminating engineering is more 
an art than a science, and to master it properly re- 
quires considerable experience and knowledge of many 
factors which can only be hinted at in a work of this 
kind. By means of the hints given out and the tables 
following, anyone, however, should be able to design 
a pretty satisfactory installation where ordinary com- 
mercial effects are desired. Where special effects in 
illumination of statuary, altars, etc., is desired, experi- 
ments with temporary lights should be made. The 
main requisite, where economy is not too much insisted 
upon, is plenty of capacity. It is never advisable to 
figure illumination for light colors, since colors are 
apt to be changed. If there is plenty of circuit ca- 
pacity, a wide choice as to candle power of lamps *s 
possible and many experiments may be made until the 
most satisfactory effects are obtained. In addition to'* 
the matter contained in this chapter, practical hints 
on the illumination of special places are given in the 
alphabetical order of locations referred to, and it is 
advisable to consult these before deciding upon any 
work. 

The circuit capacity necessary to be installed to 
arrange for any degree of illumination can be deter- 



104 ELECTRICAL TABLES AND DATA 

mined readily by reference to Table XXXI. Multiply 
the floor area to be illuminated by the number of watts 
per square foot recommended with the various illumi- 
nants and by the foot candles desired. The result will 
give the number of watts for which provision should 
be made. Except in special cases (see National Elec- 
trical Code Rules) one circuit at least should be pro- 
vided for each 660 watts. If large units are used, the 
first cost will be less, but evenness of illumination will 
be sacrificed unless lamps can be hung high. 

The intensity of illumination obtainable from a 
given source varies with the height and distribution 
of lamps; condition, type and kind of reflectors or 
enclosing globes; nature and color of ceilings and 
walls; also with the voltage maintained, and is never 
quite the same at all parts of the working plane. 

The figures given below are intended as approxima- 
tions and for quick determination of the number of 
lamps required. The watts per square foot given in 
connection with the various illuminants are thought 
to be sufficient to provide an illumination of one foot 
candle ; for greater intensities they must be multiplied 
by the number of foot candles desired. 

Table XXXII is prepared to illustrate the difference 
in the quantity of wiring material required for illumi- 
nation brought about by the use of large and small 
units or clusters of lamps. The line "Wire used per 
sq. ft." refers only to the wire (one leg) used between 
lamps. The wire needed to feed the circuits must be 
separately calculated. In case of arc lamps, or large 
incandescent lamps using one per circuit, no wire 
between lamps will be used. No allowance is made for 
switches or drops to brackets and it is assumed that 
circuits are run according to N. E. C. rules, never more 
than 660 watts per circuit. The table is not quite 
accurate unless the space illuminated is of such size as 
to allow of the use of full circuits. 



ELECTRICAL TABLES AND DATA 



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108 ELECTRICAL TABLES AND DATA 

Average illumination, if made up of spots of very 
bright light alternating with low illumination, is no 
criterion of the value of illumination. The very bright 
spots only make the others appear less brilliant. The 
eye has great powers of adjustment and can get along 
with low illumination if it is even, but with elderly 
persons it cannot rapidly and often change its adjust- 
ment without causing pain and injury. The quantity 
of illumination should be adjustable, for not all per- 
sons can be comfortable with the same intensity. The 
source of light should never be visible, especially if it 
is of high intrinsic brilliancy. The best light is one 
sufficiently diffused to cast but a slight shadow. In 
offices, however, where one source of light must serve 
many persons, an absolutely shadowless inverted light 
is desirable. It is good practice to space outlets so 
that the space between lamps is from one to two times 
the height of lamps above the working plane. This 
rule requires large units for high ceilings and small 
ones for low places. Special reflectors, however, have 
a certain ratio of spacing to height which should be 
obtained from the maker. Buildings containing many 
windows require more artificial light for night work 
than the ordinary building. 

The following tables are based on Holophane 
Intensive, or medium reflectors, and will give fair 
approximations of results to be expected from other 
reflectors. Holophane reflectors are of high efficiency 
and in some cases allowance must be made for this. 

Incandescent Lamps. — These lamps are operated 
mostly in multiple, and when so used never at a higher 
voltage than 250. On series circuits the voltage used 
runs into the thousands, but special lamps are re- 
quired. Most lamps are built marked with three 
voltages: top, middle, and bottom. The top voltage is 
■preferably used ; with this voltage the efficiency is 
the highest but the life shortened; with botton voltage 



ELECTRICAL TABLES AND Di 
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TABLE XXXV 

rn Table Showing Illumination in Foot Candles from 25, 40 and 
3 Tungsten Lamps Arranged in 3 Eows at Heights and Distances 
as Given in Table. Bowl Frosted Lamps Equipped with Holo 
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ELECTRICAL TABLES AND DATA 115 

the opposite will be the case. See Table XXXIX for 
approximate effects. 

The efficiency of all lamps decreases with use. In- 
candescent lamps will not give good results with fre- 
quencies lower than 40 ; for outdoor illumination they 
have, however, been used with 25 cycles. The fluctua- 
tions are less noticeable with heavy filaments. 

Circuit Limitations. — Not more than 660 watts are 
generally allowed on circuits, but where small fixture- 
wire and fiber lined sockets and flexible cords are not 
used there is no serious objection to 1320 watts per 
circuit, or 32 lights instead of the usual 16. 

Frosting. — Lamps are frosted to reduce the intrinsic 
brilliancy and through it become less harmful to the 
eye. Ordinary frosting reduces the c.p. from 5 to 10 
per cent, but shortens the life from 25 to 50 per cent. 
Bowl frosting has no appreciable effect upon the life. 
The effect of coloring upon the life of the lamp is. 
about the same as that of frosting. The effect upon 
the c. p. varies with the color and its density. Amber,, 
opal and yellow absorb the least ; blue, green and pur- 
ple the most; blue and red are the most used colors. 
Not much illumination can be expected from colored, 
lamps. In some cases lamps are merely bowl colored. 
The efficiency of incandescent lamps increases with 
the voltage, but the length of life decreases. To a 
certain extent, therefore, what is gained on the one 
hand is lost on the other. 

Table XXXIX is prepared to facilitate the calcula- 
tions necessary to be made in order to determine the- 
most economical voltage at which to operate lamps. 
In the column "K. "W*. wasted" we give the K. W- 
wasted by the use of the middle or bottom voltage 
during the length of life corresponding to top voltage, 
which is considered the standard. In the column- 
headed "Saving in lamp renewals" we give the per- 
centage of lamp renewals avoided by the use of lamps 



116 ELECTRICAL TABLES AND DATA 

at the lower voltages. In order to find the money value 
of the watts wasted by any lamp we must multiply the 
figure given in the table by the c. p. of the lamp and 
the rate per K. W. In order to find how much the 
same combination will save us in lamp renewals we 
must multiply the cost of lamp by the figure in the 
column on "Saving in lamp renewals." If our calcu- 
lation shows a net saving it will be more profitable to 
use the lower voltage, otherwise use the higher. Ex- 
ample: With energy at 5 cents per K. W. and 25 
watt tungsten lamps costing 20 cents each, is it more 
economical to use the middle voltage than the top volt- 
age? A 25 watt lamp gives 20 c.p. and the K. W. 
wasted at middle voltage is 0.050; we have therefore 
20x0.050x0.05, which equals 0.05, or 5 cents wasted 
during 1,000 hours. On the other hand, we save 
0.23 x 0.20, which equals 0.046. The saving in cost of 
lamp renewals does not quite offset the loss by the 
lower voltage, hence the higher voltage is more 
economical. 

In many cases such a calculation has merely an 
academic value. As long as the parties using the light 
are satisfied with that obtainable from the use of 
the lower voltage there is no economy in using the 
higher. 

Smashing Point.- — The useful life of a lamp is gen- 
erally considered to be over when its c. p. has dropped 
to 80 per cent of its original value. 

The following table is based on average values. 
The improvement in lamps is at times very rapid and 
in case great accuracy is required the manufacturers" 
guaranteed data should be obtained and used instead 
of values here given. 

Inductance. — This is that property of an electric 
circuit which causes a current in it to create lines of 
force and thus produce a counter e. m. f . proportional 
to the rate of change of that current. 



ELECTRICAL TABLES AND DATA 



TABLE XXXIX 



Comparative cost of illumination and lamp re- 
newals. 



Name of 
Lamp 

Mazda or 
Tungsten 

Tungsten 
Gas Filled 



Tantulum 

Gem or 

Graphitized 

Filament 



Carbon 



Carbon 



Saving 
Voltage Watts Hours of K.W. in Lamp 
Eating Per C.P. Life Wasted Renewals 

Top 1.22 1,000 

Middle 1.27 1,300 0.050 0.23 

Bottom 1.33 1,700 0.110 0.41 

Top In large units the type " C ' ' or 

Middle gas filled lamp is fully twice as 

Bottom efficient as the common tungsten 

lamp but in connection with 
small units there is no saving, 
but a whiter light is obtained. 

Top 1.84 800 

Middle 1.91 1,075 0.056 0.26 

Bottom 2.00 1,350 0.128 0.41 

Top 2.50 500 

Middle 2.65 700 0.075 0.28 

Bottom 2.83 1,000 0.165 0.50 

Less Than 50 Watts 

Top 3.16 750 

Middle 3.40 1,100 0.180 0.68 

Bottom 3.61 1,600 0.337 0.47 

50 Watts and Over. 

Top 2.97 650 

Middle 3.18 925 0.136 0.30 

Bottom 3.39 1,425 0.273 0.54 



W ELECTRICAL TABLES AND DATA 



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TABLE 


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Tables showing 


dimensions of porcelain 


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1 


13 


f 


11 


1 


f 


00 


15 


1ft 


If 


ft 


1 


2 


20 


•2 


2 


ft 


1 


00 


21 


21 


2 


1 


ft 


1 


22 


If 


21 


l 


ft 


350,000 


23 


H 


H 


I 


1 


350,000 


24 


If 


11 


ft 


s 


00 


25 


11 


11 


11 


1ft 


400,000 


26 


2 


21 


- f 


ft 


1 


29 


2| 


■2J 


1 


If 


450,000 


36 


If 


If 


1 


f 


0000 


39 


If 


21 


f 


If 


450,000 



Split knobs are made only for wires from 14 to 8. 



ELECTRICAL TABLES AND DATA 




wills 







t» 3 



Figure 7. — Porcelain Insulators. 



ELECTRICAL TABLES AND DATA 

TABLE XXXXII 
One Wire Cleats. 











Smallest Size of" 










Wire to Fill 










Out Groove 


[eight 


Width 


Length 


Groove 


B. & S. 


li 


f 


2 


I 


8 


Hi 


f 


2 


§ 


8 


if 


1 


2| 


1 


3 


2* 


1 


21 


J 


3 


If 


u 


2| 


f 


1 


2i 


l* 


2+ 


f 


1 


n 


1A 


2f 


f 


000 


2* 


1A 


2f 


f 


ooo- 


21 


1A 


3 


tt 


250,000 


2H 


1A 


3 


11 


250,000 


3i 


if 


3| 


u 


6,000,000 


3f 


1A 


3« 


if 


750,000 


3f 


If 


4f 


2 


2,000,000 


4 


2 


'5 


11 


1,750,000 


4 


2 


5 


1* 


1,000,000 



Two Wire Cleats 
I' li I 3| A M 

Three Wire Cleats 

1* I 3| A 14 

* The wire sizes given are thought to be the smallest the 
cleats will grip well. Diameters of wires, however, vary 
considerable and some single braid wires may be too small 
for the cleats with which they are supposed to go. See 
tables giving diameters of insulated wires. 

Insulating Materials. — The standard insulating 
materials are glass, porcelain, slate (without metal 
veins), marble, clay and certain compositions. The 
general requirement is that materials to be used for 



122 ELECTRICAL TABLES AND DATA 

insulation shall be incombustible, shall not absorb 
moisture and shall not soften from heat. Wood and 
fiber are not approved, but are tolerated in some cases. 

The dimensions and other data concerning insu- 
lators, cleats and tubes are given in Tables XXXX 
to XXXXII. 

In buildings insulators must provide \ inch separa- 
tion between supports and wires and in damp places 
1 inch is required. 

Below are given sizes of bushings constructed ac- 
cording to the N. E. Code standard. Also the largest 
sizes of wire that can be used in them. The diameters 
of wires vary somewhat, and while it is believed that 
trie wires given can be readily drawn through the 
bushings, it is advisable to use a larger bushing where 
it is necessary to draw wires through many of them, 
as in concealed knob and tube work. 

Logarithms. — Logarithms are used for multiplica- 
tion and division of large numbers, for raising num- 
bers to any power or extracting roots. Every log- 
arithm of 'the number 10 or greater than 10 consists 
of two parts. — a whole number, which is known as the 
characteristic, and a decimal fraction known as the 
mantissa. The mantissa of all numbers consisting of 
the same digits is the same ; thus in the table (which 
gives only the mantissa) we see that 0.8, 8, and 80 
each have the same mantissa, viz., .903 09, and this 
mantissa would still be the same for 800 or 8000. The 
characteristics of these numbers, however, are not the 
same, but always 1 less than the number of integers 
or whole numbers ; thus for 8 it would be 0, for 80 it 
would be 1, making the logarithm of 8 = 0.903 09 and 
that of 80=1.903 09. If the number of which the 
logarithm is to be taken is less than unity, the charac- 
teristic is 1 greater than the number of ciphers which 
follow the decimal point. The characteristics of vari- 
ous numbers are given below. The characteristic of 






ELECTRICAL TABLES AND DATA 123 

a number does not change unless that number be in- 
creased or decreased by one decimal place. 

1 000 000 = 6 

100 000 = 5 

10 000 = 4 

1 000 = 3 

100 = 2 

10 = 1 

1 = 

0.1 = 1 

0.01 = 2 

0.001 = 3 

0.0001 = 4 

The characteristics of logarithms of numbers less 
than 1 are treated as minus quantities and usually 
designated by drawing a line above them. 

The characteristics serve merely to determine the 
location of the decimal point. Whether they are added, 
subtracted or multiplied, if they are positive we must 
add to the number (found as hereafter described) 
ciphers enough so that the whole number will contain 
one more integer than the characteristic indicates. If 
the characteristic is minus, we must prefix one cipher 
less than the characteristic indicates. 

How to Find the Logarithm of a N 'umber. — Trace 
along first column at the left until the first two digits 
of the desired number are found; next follow along 
the same horizontal line until the third digit is found. 
At this place the mantissa required will be found. 
Put this down, prefixing it with a decimal point, and 
in front of it place a number equal to one less than 
the number of digits composing the original number. 
Example : find the logarithm of 676. Tracing down 
the left hand column, we come to the number 67 and 
in this horizontal line until we come to the third num- 
ber, 6, we find 829 95. As 676 contains 3 digits our 



124 ELECTRICAL TABLES AND DATA 

characteristic is 2 and we have 2.829 95, which is the 
logarithm of 676. 

How to Find a Number Corresponding to a Certain 
Logarithm. — This is accomplished by the reverse proc- 
ess. Suppose we wish to find the number whose log- 
arithm is 1.421 60 ; we first look for the mantissa part 
of it and find it in the horizontal line with 26 and 
under 4, giving us 264 as the required number; since 
the characteristic is 1 we locate our decimal point 2 
places from the left and the actual number now is 26.4. 

To Use Logarithms for Multiplication. — Find the 
logarithms of the two numbers; add them and find 
the number corresponding thereto. Example : What 
is the product of 36 x 88 ? 

log. 36 = 1.556 30 

log. 88 = 1.944 48 

3.500 78 

The mantissa nearest equal to 500 78 is 499 69, 
which corresponds to 316. Since our characteristic is 
3 we point off 4 from the left, giving us the number 
3160. 

To Divide by Logarithms. — Find the logarithms of 
the two numbers as before and subtract one from the 
other and find the number corresponding to the 
remainder. 

To Raise a Number to Any Power.— Find the log- 
arithm and multiply it by the index of the power. 
Example : "What is the cube of 9 ? 

Log 9 = .954 24; this multiplied by 3 = 2.862 72; 
looking to the table we find 862 73 as the nearest and 
this corresponds to 729, and as our characteristic is 2 
we point off 3 from the left, which shows us that the 
desired number is 729. 

To Extract Roots. — Find the logarithm of the num- 
ber as before and divide by the index. Example: 
What is the cube root of 1331 ? The number 1331 is 



ELECTRICAL TABLES AND DATA 125 

not tabulated, but the mantissa of 133 will be the 
same and it is 123 85 with a characteristic of 3, mak- 
ing it 3.123 85; this divided by 3 = 1.041 28, and the 
number corresponding to this is 11 ; since our char- 
acteristic is 1 we point off 2 from the left. 

The method of dealing with quantities less than 
unitv is explained by the following example : What 
is the product of 0.079x0.87? The log of 0.079 is 
897 63 and as there is one cipher following the 
decimal point our characteristic is 2; the log of 0.87 
is 939 52 and as there is no cipher after the decimal 
point the characteristic is 1. We now add the man- 
tissae and the characteristics separately, and as the- 
only characteristics are minus quantities, we subtract 
the positive characteristic found by adding the man- 
tissae from the sum of the negative characteristics, 
with the net result as given below: 

2 .897 63 
1 .939 52 



3 1.837 15 
1 

2.837 15 

The nearest number in the tables to 837 15 is 
836 96 and this we see corresponds to the number 
688. As our characteristic is now 2 we prefix this, 
number with one cipher, giving us 0.0688 as our 
product. 

In case the mantissa is not tabulated and the near- 
est one to it is not considered accurate enough, the- 
approximate value of the corresponding number can, 
be found by taking the numbers corresponding to the 
nearest two mantissae and noting their difference. 

Multiply this difference by -r- where a is the difference 
o 

between the lowest mantissa and the one under con- 



126 ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 

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130 



ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 131 

sideration, and h the difference between the two man- 
tissae; next add this number to the lower number. 
Example : Our mantissa is 2.851 60, and looking into 
our table, we find that it is not tabulated. The next 
lower is .851 26, which corresponds to the number 700 ; 
the next higher is 2.851 87, which corresponds to 710. 
Now, .851 60- .851 26 leaves us 34, and the difference 
between 851 26 and 851 87 is 61. We have now 

34 

-^ x 10, which equals 5.57, and this added to 700 gives 
oJ 

us the approximate value of the number correspond- 
ing to the mantissa of 2.851 60, viz., 705.57. 

Magnetic Blowout. — A strong magnetic field repels 
an arc and is often used to break it. It is made use of 
in lightning arresters, and at other places where the 
arc is troublesome. 

TABLE XXXXIV 

Melting Points of Various Substances in Degrees Centigrade 
and Fahrenheit 

C. F. v C. F. 

Aluminum 659 1218 Mercury —38.7—37.7 

Antimony 630 1166 Nickel 1452 2645 

Bismuth 271 520 Paraffin 52 126 

Brass 900 1652 Photo emulsion . . 32 90 

Bronze 900 1652 Platinum 1755 3191 

Carbon 3600 6512 Eubber 100 212 

Chronium 510 950 Silenium 218 424 

Cobalt 1490 3714 Silicon 1420 2588 

German Silver. -1100 2012 Silver 960 1760 

Glass 1300 2372 Steel, Av. ... . . .1400 2552 

Gold 1063 1945 Sulphur 110 230 

Gutta Percha... 100 212 Tantalum 2850 5162 

Iridium 2300 4140 Tin 232 449 

Iron 1520 2768 Tungsten 3000 5432 

Lead 327 620 Vanadium 1730 3146 

Manganese 1225 2237 Wax, Bees 62' 143 

Marble 2500 4532 Zinc 419 787 

Bureau of Standards as authority for the majority. 



132 



ELECTRICAL TABLES AND DATA 



Mains. — This term properly used applies only to 
the last set of wires feeding the final distribution point. 
Primary mains are those which feed the individual 
transformers. The wires leading from transformers 
are usually spoken of as secondary mains, although 




*\l 

Figure 8. — Measurement of Heights and Distances. 



there may be conditions in which they would be sec- 
ondary feeders. 
Measurement of Heights and Distances. The 

measurement of heights and distances requires first 
of all the use of right angles. Where no instruments 
or squares are available, a right angle can be laid out 
as in G, Figure 8, setting stakes or stretching lines so 



ELECTRICAL TABLES AND DATA 13£ 

that the dimensions given, or multiples of them, obtain 
on the three sides. 

A square or rectangle can be proved by stretchings 
diagonals from the corners. When both diagonals are 
the same length we have a perfect rectangle. See H, 
Figure 8. 

The height of a pole or other object can be found 
by the method shown in 7, Figure 8. Set up two 
stakes, A and B, a known distance apart and of a 
height so that their tops form a straight line with top 
of pole. When this is done the length of pole C above 

B is to E as D is to F, hence C = — Er . If the total length 

r 

ofD + Fis made equal to 27J feet and F-2\ feet, then 
C = 10xi£. Add distance below line D to this to ob- 
tain total height of pole. 

The distance between two points, one of which is 
accessible, can be found by means of the construction: 
shown in J, Figure 8. Similarly to the foregoing, 
if B is made 10 times C, then A will be made 10' 
times D. 

The distance between two inaccessible points may 
be measured by the methods shown in K, Figure 8.. 
If two stakes, C and D, be set up with reference to 
A and B, so as to be at right angles to each other and 
with diagonals pointing to A and B, also forming the 
same angles, the distance between C and D will be: 
equal to that between A and B. 

Another method consists in setting up two stakes,, 
E and F, and parallel to them drawing a line or lay- 
ing a tape line upon the ground and setting up stakes: 
as indicated at S. Measure distances between the 
various stakes and draw a plan of them to any con- 
venient scale as indicated. Measure the distance be- 
tween A and B on this plan. This method does not 
require that E and F be parallel or centered with 
reference to A and B. 



134 



ELECTRICAL TABLES AND DATA 



Mensuration. — 

Area of a triangle = base x \ altitude. 

Area of a parallelogram = base x altitude. 

Area of a trapezoid = altitude x \ the sum of parallel 
sides. 

Area of trapezium: divide into two triangles and 
find area of the triangles and add together. 

Area of circle = diameter 2 x 0.7854 = radius 2 x 3.1416. 

Area of sector of circle = length of arc x \ the radius. 

Area of segment of circle = area of sector of equal 
radius -area of triangle, when the segment is less, 
and + area of triangle when the segment is greater 
than the semi-circle. 

Area of circular ring = diameters of the two circles x 
difference of diameters x 0.7854. 

Area of an ellipse = product of the two diameters x 
0.7854. 

Area of a parabola . = base x f altitude. 

Area of regular polygon = sum of its sides x perpen- 
dicular from its center to one of its sides -r- 2. 



REGULAR POLYGONS 

















Length 














Radius 


of 










Length 




of side when 






Area 




of 




circum- 


radius 






when 




side 


Perpen- 


scribed 


of 






dia. of 


Area 


when 


dicular 


circle 


circum- 


No 




inscribed 


when 


perpen- 


when 


when 


scribed 


of 




circle 


side 


dicular 


side 


side 


circle 


i Sides 


=1 


=1 


=1 


=1 


=1 


=1 


3 


Triangle 


..1.299 


0.433 


3.464 


0.289 


0.577 


1.732 


4 


Square .. 


..1.000 


1.000 


2.000 


0.500 


0.707 


1.414 


5 


P'entag. . 


..0.908 


1.720 


1.453 


0.688 


0.851 


1.176 


6 


Hexag. .. 


..0.866 


2.598 


1.155 


0.866 


1.000 


1.000 


7 


Heptag. . 


..0.843 


3.634 


0.963 


1.039 


1.152 


0.868 


8 


Octag. . . 


..0.828 


4.828 


0.828 


1.207 


1.307 


0.765 


9 


Nonag. . . 


..0.819 


6.182 


0.728 


1.374 


1.462 


0.684 


10 


Decag. . . 


..0.812 


7.694 


0.650 


1.539 


1.618 


0.618 


11 


Unclecag. 


..0.807 


9.366 


0.587 


1.703 


1.775 


0.563 


12 


Dodecag. 


..0.804 


11.192 


0.536 


1.866 


1.932 


0.518 



ELECTRICAL TABLES AND DATA 135 

Surface of cylinder or prism = area of both ends-f 

length x circumference. 
Surface of sphere = diameter x circumference. 
Convex surface of segment of sphere = height of seg- 
ment x circumference of the sphere of which it is a 

part. 
Surface of pyramid or cone = circumference of basex 

-| of the slant height + area of the base. 
Surface of frustrum of cone or pyramid = sum of cir- 
cumference at both ends x | of slant height + area of 

both ends. 
Contents of sphere = cube of diameter x 0.5236. 
Contents of cylinder or prism = area of end x length. 
Contents of segment of sphere = (height + three times 

the square of radius of base) x (height x 0.5236). 
Contents of frustrum of cone or pyramid: Multiply 

areas of two ends together and extract square root. 

Add to this root the two areas x -J altitude. 
Contents of a wedge = area of base x \ altitude. 
Circumference of circle = diameter x 3.1416. 
Circumference of circle- radius x 6.2832. 
Circumference of circle = 3.5446 x square root of area 

of circle. 
Circumference of circle x 0.159155 = radius. 
Circumference of circle x 0.31831 = diameter. 
Circumference of circle x 0.225 = side of inscribed 

square. 
Circumference of circle x 0.282 = side of an equal 

square. 
Half the circumference of circle x half its diameter— 

its area. 
Square of circumference of circle x 0.7958 = area. 
Diameter of circle x 0.86 = side of inscribed equilateral 

triangle. 
Diameter of circle x 0.7071 = side of an inscribed 

square. 
Diameter of circle x 0.8862 = side of an equal square. 



136 ELECTRICAL TABLES AND DATA 

Diameter = 1.1283 V square roo ^ f area f circle. 
Length of arc = number of degrees x 0.017453. 
Degrees in arc whose length equals radius, 57.2958°. 
Length of arc of 1° = radius x 0.017453. 

Meter Capacity. — It is a general rule to install 
meters of about one-half the capacity of the connected 
load in residences ; three-fourths this capacity in small 
stores, offices, etc., and full capacity for elevator 
motor service and similar installations where exces- 
sive starting currents are the rule. For more exact 
determinations, see Demand Factors. 

The d. c. meter is essentially a shunt motor, and its 
direction of rotation is independent of the polarity, 
but if fed from the wrong side, it will run backwards. 
On a. c. circuits wattmeter readings will not check 
with volt and ammeter reading; the latter must be 
multiplied by the power factor. Current transform- 
ers are used in connection with large capacity a. c. 
meters. 

Meter Location. — Meters must always be* accessi- 
ble, never in places that are locked or where meter 
readers would cause annoyance to occupants. The 
location selected must be free from moisture and 
vibration. Meters should not be placed on curb walls 
of streets on which cars operate nor on thin partitions. 
If meters are placed in cabinets, these should be fire- 
proofed and no magnetic material should be brought 
close to the meter. Meters must be set level and level- 
ing can be accomplished by placing a small weight 
upon disk, and shifting meter until disk remains at 
rest in any position. In order that meters may be 
properly set, meter boards must be provided. The 
necessary dimensions of such boards vary with the 
service to be rendered and are given on Figures 9 and 
10. These are the requirements in force in the City 
of Chicago. 



ELECTRICAL TABLES AND DATA 

A o 




ALTERNATING 



~\& 



22 



WATT 
HOUR 
METER 




34 




r 


{ \ 
i ' 

;::5L.. ; 

i i ' ! 

• i 

• i 

i i ; i 
^ / x , { 


34^ 




LJ lJ 


N/ 




k— »e* — » 





Figure 9. — Meter Fittings and Meter Boards. 
Figure 9. — Showing Proper Location of Meter Fittings and 

Size of Meter Boards Kequired for Different Installations. 
A. C. Eesidence or Apartment Lighting. 

30 sockets or 1500 watts, or under, sketch A. 

31 to 48 sockets or 1501 to 2640 watts, sketch B or D. 
Above 48 sockets or 2640 watts, sketch C or E. 



ELECTRICAL TABLES AND DATA 



A. C. Business Lighting. 

24 sockets or 1320 watts, or under, sketch A. 

Above 24 sockets or 1320 watts, sketch C or E. 
A.. C. Power. 

5 H. P., and under, single-phase, sketch A. 

Above 5 H. P., and all three-phase, sketch C. 

P i 






Q 


> ^ 


< -, 






22 


■ i : K ) 




^J 


V 


r-"f — i 




'^-w — > 



DIRECT CURRENT 



/< 


i 


-i f 

; r""""i i 




.2 




'! i ' 






u 


Uf~-\ 


• i 


>/ 




rn 






k — 


— **- 


* 




Figure 10. — Meter Fittings and Meter Boards. 



ELECTRICAL TABLES AND DATA 139' 

Figure 10. — Showing Proper Location of Meter Fittings and 

Size of Meter Boards Eequired for Different Installations. 
D. C. Eesidence or Apartment Lighting. 

30 sockets or 1500 watts, or under, sketch F. 

31 to 48 sockets or 1501-2640 watts, sketch G or I. 
Above 48 sockets or 2640 watts, sketch E or J. 

D. C. Business Lighting. 

24 sockets or 1320 watts, or under, sketch F. 
Above 24 sockets or 1320 watts, sketch H or J. 
D. C. Power. 

1500 watts, or under, sketch F. 
Above 1500 watts: 

2 -wire, sketch G or I. 
3-wire, sketch H or J. 

If the meter is located at service entrance, the meas- 
ured energy will exceed the delivered energy by the 
percentage of loss occurring in the feed wires. If it 
is located at some distance from this point the service 
company will stand part or all of this loss. 

The per cent loss per 100 feet ran with . different 
voltages, wires assumed to be loaded to full capacity 7 
is given in Table XXXXV. 



TABLE XXXXV 



B. & S. 


Amperes 


110 v. 


220 v. 


440 v. 


550 v. 


1000 i 


14 


15 


4.80 


2.40 


1.20 


0.96 


0.53 


12 


20 


5.80 


2.90 


1.45 


1.16 


0.64 


10 


25 


4.50 


2.25 


1.13 


0.90 


0.50 


8 


.35 


4.00 


2.00 


1.00 


0.80 


0.44 


6 


50 


3.60 


1.80 


0.90 


0.72 


0.40 


5 


55 


3.10 


1.55 


0.77 


0.62 


0.34 


4 


70 


3.10 ' 


1.55 


0.77 


0.62 


0.34 


3 


80 


2.90 


1.45 


-0.73 


0.58 


0.32 


2 


90 


2.60 


1.30 


0.65 


0.52 


0.29 


1 


100 


2.20 


1.10 


0.55 


0.44 


0.24 





125 


2.20 


1.10 


0.55 


0.44 


0.24 


00 


150 


2.10 


1.05 


.0.53 


0.42 


0.23 


000 


175 


1.90 


0.95 


0.47 


0.38 


0.21 



0000 225 1.90 0.95 0.47 0.38 0.21 

300 000 275 1.90 0.95 0.47 0.38 0.21 



140 ELECTRICAL TABLES AND DATA 

Reactances are not taken into consideration. 

Meters, Maximum Demand. — The cost of supply- 
ing electrical energy is properly divided into two 
parts: One of these consists in charges to be made 
for meter reading, bookkeeping, and investment of 
capital ; the other in the cost of energy consumed by 
the customer. 

The capital investment depends largely upon the 
maximum demand of the customer and also upon the 
time at which this demand occurs. A given trans- 
former, for instance, will serve perhaps twice as many 
families in which the ironing is done during the day, 
as it will where an iron is used at the same time with 
the lights. In order to obtain compensation for un- 
necessarily high demands for short times, maximum 
meters are installed, or a certain fixed charge per 
month is made against every customer whether cur- 
rent is used or not. 

The maximum demand meter may be any arrange- 
ment which will indicate the highest amperage, or 
rate of power consumption, during any month or 
other convenient term. The method of computing 
Dills where these meters are installed is somewhat con- 
fusing to one who does not make a business of it, and 
to show the influence of max. meters the following 
table is presented : This table shows the average rate 
per K. W. hour brought about by different maximum 
demands and total K. W. consumption per month. 

TABLE XXXXVI 



Max. Amp. 






Total K.W. 


Hours 










25 


50 


75 100 


125 


150 


200 


300 


25 


11. 


11. 


11. 10.1 


9.3 


8.7 


7.7 


6.4 


.20 


11. 


11. 


10.4 9.3 


8.6 


8.0 


7.0 


6.0 


15 


11. 


11'. 


9.3 8.4 


7.9 


6.9 


6.2 


5.5 ' 


10 


11. 


9.3 


8. 7. 


6.4 


6. 


5.5 


5. 


.5 


9.3 


7. 


6. 5.5 


5.2 


5. 


4.7 


4.4 



ELECTRICAL TABLES AND DATA 



This table is based on a charge of 11 cents per K. W. 
hour for the first thirty hours of the maximum used ; 
6 cents per K. W. hour for the next thirty hours of 
the maximum, and 4 cents per hour for the balance. 
The maximum load is found by multiplying the high- 
est amperage during the month by the volts. If we 
have a maximum of 10 amperes our first charge will 
be 10 x 110x30x0.11 = $3.63; the next will be 10 x 
110x30x0.06 = $1.98, and for the remaining K.W. 
hours we charge 4 cents, which equals $1.60, giving us 




<L 



Figure 11. — Meter Dials. 

a total of $7.21 for the 100 K. W. hours used, or ap- 
proximately 7 cents per K. W. In the table the change 
in rates per K. W. is shown as affected by the propor- 
tion between the maximum demand and the total 
consumption. 

Meter Reading. — This is a very simple matter 
when one has become accustomed to it, but is very 
confusing to those who have not had it to do. Most 
meters have five dials arranged somewhat on the order 
shown in Figure 11. These dials are all connected 
by gearing and serve merely as counters. The one at 
the right is driven by the meter mechanism proper, 
and through it the others are driven in turn. In the 



142 ELECTRICAL TABLES AND DATA 

whole train each one revolves in a direction opposite 
to that of the one driving it, as indicated by arrows 
and also by the numbers used. The proportion of the 
gearing" is such that while the pointer on the driving 
dial makes one complete revolution, the one on the 
next dial to the left makes only one-tenth of one 
revolution. From this it follows that any pointer, 
except the one at the extreme right, can be fully on 
any number only at the same time that the pointer to 
the right of it is on 0. This is the principal point to 
bear in mind in meter reading. In Figure 11 a com- 
plete revolution of any pointer indicates the use of 
the number of watt hours found at the top of that 
dial. Meter reading is best begun by noting the read- 
ing of the dials from right to left, although persons 
who have become accustomed to it find no trouble in 
reading from left to right. Let us begin reading our 
meter from right to left and note this rule : Put 
down the indication of the right-hand dial, and unless 
its pointer is fully on, or has just passed, 0, choose 
the lowest of the two numbers between which the. 
pointer may be on the next dial, and continue in this 
manner, putting down each number to the left of the 
last. Following out this rule we have first 900, next 
8, then another 8, after that 1, and for the fifth dial 
another 1, giving us a total of 1 188 900 watt hours. 
Striking out 3 figures at the right reduces this to 
K. W. hours. It must be borne in mind that some 
meters are arranged to read directly in K. "W. hours 
and some require the use of multipliers to determine 
the actual watts registered. 

Meter Testing'. — In large cities meter fittings are 
usually provided, for the connection of meters and 
the best of these are arranged to allow of easy con- 
nection for meter without interfering with the opera- 
tion of meters. On all meters the disk is arranged to 
make a certain number of revolutions per K. W. and 



ELECTRICAL TABLES AND DATA 143 

if this is known the load on the meter at any moment 
can be determined. The relation between the num- 
ber of revolutions of the disk and the corresponding 
dial reading may be expressed by a multiplier which 
is known as the "constant" of the meter and is usually 
marked upon the disk or somewhere near it. The 
value of this constant in any particular instrument 
depends entirely upon the gearing between the disk 
and dial. Meter constants may be expressed in the 
following ways (1) number of watt hours indicated 
by one revolution of the disk; (2) the number of watt 
seconds indicated by one revolution of the disk; (3) 
the speed in R. P.M. at full load or rated load. 

If K stands for the constant of the meter in either 
of the meanings given above and R for the number 
of revolutions made in 8 seconds, the load passing 
through the meter during any interval of time will 
be found by the following formulae : 

1. Watts = 

o 

KR 

S 
KR 

8 

The testing of meters is best done by connecting a 
standard meter in series with it, and comparing the 
readings. The test meter may be connected so as to 
measure the operating current in addition to the load 
of the one under test. In this case the meter under 
test will be found ' ' slow " if it is arranged to measure 
that current; if the test meter is connected to avoid 
this current the other will be found "fast." Before 
making any test the meters should be allowed to be in 
circuit for about 15 minutes. A stop watch must be 
used if accurate results are required. On important 



2. Watts = 

3. Watts = 



144 ELECTRICAL TABLES AND DATA 

installations it is advisable to test meters at least twice 
per year. In some cases two meters are installed in 
parallel; such meters are a constant check upon one 
another. 

Motion Pictures. — Photography. — Cooper Hewitt 
lamps are used almost exclusively for this purpose, 
and about 50,000 c. p. are required to do good work. 
Lamps must be arranged adjustable to suit whim of 
producer. 

Exhibition. — The exhibition of motion pictures may 
be carried on with one arc lamp, but it should have 
an adjustable rheostat or compensator. Many films 
are very dark, and require extra strong lighting. 
Good exhibitions require at least two machines and a 
corresponding number of arc lamps, one to be ready 
when the other runs out. Stereopticon lamps and 
spot lights must also often be provided for. It is 
customary to require at least a No. 6 wire for each 
motion picture arc, as they often draw as high as 50 
amperes. There is considerable fire and life hazard 
connected with the exhibition of motion pictures, and 
each municipality usually has some rules governing 
the handling of films and apparatus, which should be 
consulted. 

Motors. — Alternating Current. — There are four 
general types of alternating current motors; viz., in- 
duction, series, repulsion and synchronous motors. 

Induction Motors. — The stationary part of this 
motor is termed the "stator," the moving part the 
"rotor." That part of the winding which receives 
current from the supply line is known as the "pri- 
mary," the other as the "secondary." From a me- 
chanical point of view this is the simplest and best of 
all motors, and it is also the most used type. Poly- 
phase induction motors are self-starting, but single- 
phase motors require some special starting device. 
These motors are essentially constant speed motors, 



ELECTRICAL TABLES AND DATA 145 

but their operation depends upon the "slip," which 
requires a slight reduction of speed with increasing 
load. This motor has a poor starting torque and often 
requires four or five times the running current to- 
start it. 

The rotor of the common induction motor is not 
provided with any winding, but for special purposes,, 
such as printing presses, cranes, etc., wound rotors 
are often used. Resistances can be used with such 
motors and the speed also thus controlled. The speed 
will, however, be variable with the load and the motor 
will require watching. With a wound armature the 
torque is the same for all spee.ds. Auto-starters, or 
compensators, are used to start the larger motors, but 
the smaller ones may be connected directly to the 
circuit. A throw over switch fused on one side only,. 
and so connected that the starting current need not 
pass through the fuses, is generally used for medium 
size motors, up to 5 H. P. 

The synchronous speed of an induction motor can 
be found by the formula: 

R p M 60 x frequency 

number of pairs of poles 

Below is a tabulation of all possible speeds of syn- 
chronism of 60 and 25 cycle motors with the numbers 
of poles given : 

Number Poles 60 Cycles 25 Cycles. 

2 3600 1500 

4 1800 750 

6 1200 500 

8 900 375 

12 600 250 

16 450 187% 

24 300 125 

Actual speeds, on account of "slip," are from 3 to 
10 per cent lower. 



146 ELECTRICAL TABLES AND DATA 

Repulsion Motor. — The field winding of this motor 
is similar to that of a single-phase induction motor. 
There is no connection whatever between it and the 
armature, and the latter is always wound and pro- 
Tided with a commutator and short-circuiting brushes. 
The currents induced in the armature always tend to 
oppose those in the field, hence the name, repulsion 
motor. The speed of this motor is variable with the 
load and may be above synchronism, but the operation 
at this speed is not satisfactory. In some types the 
direction of rotation, speed, regulation, and stopping 
and starting may all be accomplished by simply shift- 
ing the brushes. Some single-phase motors are ar- 
ranged to start as induction repulsion motors. When 
the motor is up to speed, the brushes are automatically 
thrown off, and the motor continues to run as a sim- 
ple induction motor. The starting current of this 
type of motor is from two to three times the full load 
current and the starting torque is good. 

Reversing Direction of Rotation, — The synchronous 
motor is not self-starting, and will run in whichever 
direction it is started. It is usually started by a small 
induction motor, and to reverse its direction of rota- 
tion the connections of the latter must be changed. 
Polyphase synchronous motors may be started by turn- 
ing on the a. c. current while the d. c. fields are open. 
In such a case the direction of rotation can be changed 
by reversing two-phase wires in the same manner that 
induction motors are reversed. To reverse the direc- 
tion of rotation of a two-phase motor, the two wires of 
■one phase must be changed. If there are only three 
wires the connections must be changed so that the 
relative direction of current through one of the phases 
is reversed. 

Three-phase induction motors are reversed by 
changing the connections of any two-phase wires. 
The direction of rotation of a single-phase induction 



ELECTRICAL TABLES AND DATA 147 

motor is indeterminate unless it is provided with some 
special starting apparatus. Some may be started by 
hand and will run in whichever direction they are 
started; others require that the connections of the 
starting coils (not starting box) be reversed. The 
alternating current series motor may be reversed in 
the same manner as d. c. motors. The repulsion motor 
may be reversed by either shifting the brushes or re- 
versing the field connections. 

Series' Motor. — This type of alternating current 
motor has about the same general characteristic as the 
direct current series motor. Except in small sizes it 
cannot.be used without constant attendance. The field 
magnets are always laminated and the fields must be 
obtained with as few turns of winding as possible, as 
the self-induction increases as the square of the num- 
ber of turns of wire. Series motors may be had for 
use either on alternating or direct current circuits. 

The armature is relatively more powerful than the 
fields, and the field distortion is therefore greater than 
in direct current series motors. To regulate this,. 
many of the motors are provided with extra coils, 
some of which are in series with the fields and arma- 
tures, and others arranged to receive current only by 
induction. 

Synchronous Motors. — These motors may be either 
single of polyphase. They must run at an absolutely 
constant speed governed by that of the generator. 
This speed may be found by the formula 

60 x frequency 



number of pairs of .poles 



All synchronous motors require direct current for 
field excitation. They are not self -starting in the true 
sense of the word, and must be brought up to nearly 
the proper speed before current is finally turned on.. 



148 ELECTRICAL TABLES AND DATA 

Synchronous motors are not much used, but where 
they are used they may be made to exert a beneficial 
effect upon the power factor of the line. They cannot 
be made to start under load, and if overloaded will 
come to a stop. "Hunting" or "phase swinging" is 
one of the chief troubles encountered with synchronous 
motors. The two chief objections to synchronous mo- 
tors are : they require direct current for field excita- 
tion, and skilled attendance for starting. 

Starting of a.c. Motors. — Most synchronous motors 
are started by small induction motors and gradually 
brought up to the speed of synchronism. A synchro- 
scope is usually provided to determine when the proper 
moment to throw in switch has arrived. 

Polyphase synchronous motors may be made self- 
starting by opening the field circuit and allowing the 
line currents to pass through the armature. The arma- 
ture then creates its own fields, and begins to revolve 
on the principle of an induction motor. The speed 
gradually increases, and when it reaches about that of 
synchronism, the d. c. field circuit is closed. Where 
motors are started in this way, an ammeter should be 
in the circuit and the current observed. If the current 
grows less after the field circuit is closed, the motor is 
working properly; if otherwise, the switch must be 
opened again, and a new trial made. This method of 
starting should not be used unless it is known that the 
motor is arranged for it. Very high potentials may 
be induced and break down the insulation. 

The starting current of induction motors thrown 
directly onto the line is from three to ten times the 
normal running current, and to keep it from becom- 
ing excessive, compensators or auto-transformers are 
usually inserted in the line wires. This provides low 
voltage for starting. There are usually either three 
or four taps in the connections of an auto-transformer. 
"When only three are provided it is customary to 



ELECTRICAL TABLES AND DATA 149 

arrange them to give 50, 65, and 80 per cent of the 
line voltage. Four taps are used only with the 
largest motors and in such a case the taps are ar- 
ranged for about 40, 58, 70, and 80 per cent of the 
line voltage. Always make the connection for the 
lowest voltage at which the motor can be started. 
Modern starters are equipped with no-voltage and 
overload releases. 

Three phase motors may be connected either in 
star or delta. If the latter is the permanent connec- 
tion the switching arrangement may be such as to put 
the motor in star for starting, the switch being thrown 
over when the motor has attained some speed. In 
cases where the three transformers are near the motor 
the transformer connections may be switched in the 
same way, using the star connection to start the motor 
and throwing over to delta when it has gained somo 
in speed. 

Medium sized motors are often connected direct to 
the line without any means of reducing the voltage. 
In such cases a throw-over switch unfused on one 
'side, but properly fused on the other, is provided. 
The switch is closed on the unfused side until the 
motoV has attained its speed and is then thrown over 
to bring it under the protection of the fuses. With 
this arrangement the fuses at motor may be provided 
to fit the running current while those at the beginning 
of supply line must be large enough to stand the 
starting current which is often very excessive. 

Speed Control. — The speed of a synchronous motor 
is unchangeable and governed entirely by the fre- 
. quency and number of poles. The speed of an induc- 
tion motor varies directly as the frequency, and if we 
have means of changing this, we may obtain any 
speed desired. 

The same formula for speed which shows the above, 
also shows that the speed can be varied by varying the 



150 ELECTRICAL TABLES AND DATA 

number of poles. This is sometimes accomplished by- 
switching devices which combine poles so as to reduce 
their number by one-half. This method is not much 
used. 

The speed can also be altered by changing the volt- 
age applied to the motor. A fourth method of speed 
control consists in providing a wound armature in 
place of the ordinary squirrel cage armature and 
placing resistances in the armature windings. Some- 
times these resistances are located inside of the arma- 
ture spider, at other times the leads are brought out, 
and the resistances mounted outside of the machine. 
The loss in speed of an induction motor with increas- 
ing load is proportional to the resistance in the rotor 
circuit, and if carried too far will cause the motor to 
stop. A reduction in speed of from 15 to 20 per cent 
will cause the ordinary squirrel cage motor to stop, 
but with a wound rotor the variation may be much 
greater. The speed control of a. c. motors is never 
very satisfactory, but where it must be, the wound 
rotor method is the most practical. 

Variable Speed Arrangements of Motors. — A well" 
known method of obtaining various speeds is that 
known as the "tandem," "cascade" or concatenation 
method of coupling two motors together to obtain 
variable speed. The first motor is fed direct from the 
line through suitable starters and the currents in the 
second motor are produced in the wound rotor of the 
first. The rotor of the second motor is also wound 
and equipped with controlling resistances. Four 
speeds are obtainable. First, the natural speed of 
motor 1 running alone ; second, that of motor 2 run- . 
ning alone ; third, the speed of the two motors com- 
bined when both tend to revolve in the same direction, 
and fourth, the speed of the two motors combined 
when one tends to run in the opposite direction. . 

Connected in direct concatenation (both motors 



ELECTRICAL TABLES AND DATA 151 

tending to run in the same direction) the speed can 
be found by the formula 

R p M _ 60 x frequency 

number of pairs of poles on both machines 

When one of the rotors is connected to oppose the 
other the speed is 

R p M 60 x frequency 

difference in number of poles in the two 
machines 

If the number of poles on the two machines is the 
same, they will run at half speed when connected in 
direct concatenation. 

This method of control is not of much u&e with fre- 
quencies above 25 cycles on account of a low power 
factor. With this method, a wound rotor is also 
always employed. 

Motor Testing. — Motors may be tested to determine 
their capacity in H. P. or K. W. ; their insulation 
resistance; their heating; speed regulation, and 
efficiency. 

The H. P. capacity of a motor, other things being 
equal, depends entirely upon the current which the 
armature will stand, and this, assuming proper me- 
chanical construction, depends entirely upon the heat- 
ing. The heat generated is proportional to the square 
of the current, but the temperature of the wire is 
influenced considerably by the ventilation. The tem- 
perature also depends upon the length of time the 
current is used, and therefore the actual H. P. which 
any motor may develop depends very much upon 
whether it is to be used continuously or intermittently. 
Every motor thus has two ratings. 

The continuous rating of a motor is at present 
usually taken as the output in H. P., or K. W. which 
it can deliver continuously, with a maximum rise in 



152 ELECTRICAL TABLES AND DATA 

temperature above the surrounding air at 25° C. 
(77° F.) of not more than 40° C. (104° F.) on field 
and armature, and not more than 55° C. (131° F.) on 
commutator. The intermittent rating differs from 
this in that it allows a temperature rise of 65° C. on 
field and armature and 90° on the commutator to be 
attained in an hour's run. Motors designed to fulfill 
these requirements can be given a still higher over- 
load rating to be used in connection with apparatus 
which is in operation for only a few minutes at a 
time. The test for heating is made by a thermometer 
placed upon the parts and covered with waste to shut 
out the cooling influence of the air. The places of 
highest temperature should be selected. 

The H. P. output of a motor may be found by the 
well-known prony brake test. To make the test, adjust 
the screws until the motor speed is reduced sufficiently 
to allow the desired current through the armature. 
The H. P. of the motor can then be found by the 
formula : 

tt p ^ sxlxp 
33,000 

where s = speed of pulley; 1= length of lever from 
center of pulley to scale attachment, and p = the pull 
on scales in pounds. 

The H. P. delivered to the motor is equal to the 
product of volts and amperes, and dividing the H. P. 
developed by the motor by that delivered to it, will 
give us the efficiency. The prony brake test cannot 
well be continued long enough to test heating of 
motor, and some other form of load must be placed 
upon it. The speed regulation of a motor may be 
found by operating the motor at various loads from 
zero to maximum, and noting the changes in speed. 
In testing alternating current motors we must mul- 
tiply the product of volts and amperes by the power 



ELECTRICAL TABLES AND DATA 153 

factor, or use a wattmeter instead of volt and am- 
meters. The starting torque of a motor can be found 
in the same way as we found the H. P., but we must 
adjust the screws until the armature comes to a 
standstill. 

Motor Troubles.— 7/ the fuses blow at starting, 
contacts may be loose or dirty, or the fuses are of 
insufficient capacity. The motor may be overloaded 
or out of order in some way. The brushes may not 
be properly set. The rheostat may be manipulated 
too fast. It is usual to allow about 30 seconds to pass 
during the starting of the ordinary motor. The sup- 
ply voltage may be higher than the motor is intended 
for, or the rheostat may be too large, and not intro- 
duce sufficient resistance. The motor may be im- 
properly connected. The field circuit may be open. 
This would prevent the armature from generating the 
necessary counter e. m. f. There may be a short cir- 
cuit in the armature, or in the fields. If a short cir- 
cuit cuts out part of the field, it will indicate itself by 
undue heating and prevent the armature from pick- 
ing up. If the frequency is too low, there will be an 
excessive current; if it is too high, there will be 
insufficient current. 

If motor fails to start and the fuses do not blow y 
there may be a dead line ; test for current. 

In the case of a series motor there may be an open 
circuit in either armature or fields ; this can be in the 
armature only if a shunt motor. Insufficient tension 
or poor contacts of brushes also often prevent the 
motor from starting. In an alternating current motor 
the frequency may be too high. One or more phases 
may be open. 

Fields Running Hot. — The voltage at which ma- 
chine operates may be higher than that for which it 
was intended. Fields may be in parallel where they 
were meant to be in series. A part of the field may 



154 ELECTRICAL TABLES AND DATA 

be short circuited, or cut out by grounding. In such 
a case one of the fields will be cool while the other runs 
abnormally hot. 

Heating of Armature. — This may be caused by an 
overload; the heating increases as the square of the 
current used. There may be a short-circuited arma- 
ture coil ; if so, it will speedily show itself by burning 
out. A strong odor of heated shellac will probably be 
the first indication. Poor ventilation is often the 
cause ; many motors are. meant to operate either open 
or enclosed, and the enclosed capacity is always much 
less than the open. 

Shaft of Bearings Running Hot. — This may result 
from improper oiling, boxes too tight, shaft bent, belts 
too tight, rough bearings, or the armature may not 
be properly centered, and thus press too hard on one 
of the end collars. 

Shocks Obtained from Machine. — These may be due 
to static electricity or to grounding of some live part 
of the motor or the frame. The troubles from static 
electricity can be overcome by grounding the frame 
or fitting the belting with arresters. 

Sparking of Brushes. — This may be due to wrong 
position of the brushes. With increasing load, the 
brushes of motors must be shifted against the direc- 
tion of rotation, and, vice versa, with generators the 
opposite rule holds. The best motors, however, re- 
quire very little shifting of brushes. Rough commu- 
tator, ragged brushes, or dirty condition of either 
commutator or brushes are frequent cause of spark- 
ing. Insufficient tension is also a frequent cause of 
sparking. If the brush is too narrow it will leave one 
segment before making the proper connection with the 
next; if too wide, it will short circuit too many and 
thus cause sparking. Incorrect spacing of brushes 
will cause sparking. Compound wound motors, or 
those operating with light field, are subject to much 



I 



ELECTRICAL TABLES AND DATA 155 

sparking. To prevent this, inter-poles are often pro- 
vided. Test direction of current in series winding by- 
starting motor with shunt field open. An open circuit 
in an armature coil will cause severe sparking, which 
will occur only at a certain place on commutator. 

Motors. — Direct Current. — There are three types 
of d. c. motors ; viz., series, shunt, and compound. 

The Series Motor. — Small series motors, such as fan 
motors, can be made to work successfully under any 
conditions. Large series motors with a variable load 
require constant attendance. Lightening the load 
will allow the motor to speed up inordinately and be- 
come dangerous. Such motors are very useful where 
heavy loads are to be started, as the torque is the- 
oretically proportional to the square of the current as 
long as the fields are at a low point of saturation. 
And in all cases when the fields are not fully satu- 
rated, the torque increases faster than the current. 
The maximum torque exists at low speed and is inde- 
pendent of the voltage, depending entirely upon the 
current. 

Shunt Motors. — The shunt motor is the most used of 
all direct current motors, and if properly constructed 
operates at a fairly uniform speed for all loads within 
its capacity. Once started it requires no attention. 
It is suitable for all classes of work, except such as 
street car service where the current is often suddenly 
interrupted and as suddenly thrown on again by 
accidents to the trolley. Its starting torque is not 
as good as that of the series motor, but it is fair. The 
field strength varies with the voltage, but as long as 
this is maintained it is independent of the voltage at 
armature terminals. 

The Compound Motor. — This is a combination of 
shunt and series motor and has both windings. If 
the current in the compound winding is in the same 
direction as that in the shunt, the increased current 



156 ELECTRICAL TABLES AND DATA 

strength necessary to handle a heavy load will 
strengthen the fields and slow.the motor down. Such 
a motor is known as "cumulative" and has a very 
good starting torque. If the compound winding is in 
the opposite direction, an increased current will 
lighten the fields and cause the motor to speed up, but 
will give it a poor starting torque. The compound 
winding may be so adjusted that the motor will run 
at a very even speed for all loads within its capacity. 
A motor so connected is known as "differential." 
Owing to the fact that part of the field magnetization 
is destroyed by the series winding, the efficiency is 
somewhat low. Commutating or inter-poles are often 
inserted in d. c. motors. Such poles are provided to 
overcome the armature reaction and produce sparkless 
commutation. Motors so equipped can carry greater 
overloads. They are very useful where a good start- 
ing torque is required. Motors are further divided 
into open and enclosed types. The capacity of a 
totally enclosed motor is only about 60 per cent of 
that of the open motor. The capacity in H. P. depends 
upon whether the motor is to be used continuously or 
intermittently, and is governed by the heating limita- 
tion, the heat generated being proportional to I 2 . 

The current required by any motor can be found 
by the formula 

H. P. delivered x 746 

Current = — ^—. =- 

efficiency x voltage 

The efficiency of a motor can be found by dividing 
the input by the output. All motors are delivering 
their maximum power when the speed is such that the 
counter e. m. f . of the motor is one-half of that deliv- 
ered at the terminals. 

Reversing Direction of Rotation. — All d. c. motors 
may be reversed by changing the connections of either 
field or armature so that current passes through one 



ELECTRICAL TABLES AND DATA 157 

of them in the opposite direction. If the current in 
both is reversed the direction of rotation will remain 
as before. Most multi-polar motors may be reversed 
by shifting the brushes sufficiently; this is equivalent 
to reversing armature leads. 

Speed Control. — All d. c. motors tend to run at a 
speed which enables the armature to generate a 
counter e. m. f . equal to that of the supply. The speed 
can be varied by strengthening the field, which re- 
duces it, or weakening the field to increase it. The 
commonest method of accomplishing speed control is 
by means of resistance cut into the armature circuit. 
This method, however, causes a speed variable with 
the load, the fall in pressure at the motor terminals 
being equal to IE. Adjusting the field strength to 
regulate the speed causes much sparking at the 
brushes. This can be obviated to a large extent by 
the use of commutating or inter-poles. The armature 
current passes around these and tends to keep the 
neutral point at a certain place, thus preventing 
sparking. Speed control is further effected by switch- 
ing arrangements which enable one to connect several 
motors either in series or parallel; the parallel con- 
nection giving the higher speed and the series the 
lower. Such systems are used mostly in connection 
with d. c. street railway service. 

Starting of d. c. Motors. — All d. c. motors, except 
the small ones which are wound with a high resistance 
in armature circuit, require some extra resistance to 
keep the current down until the armature has attained 
sufficient speed to generate the counter e. m. f . which 
finally limits the current. This resistance must never 
be in the field circuit of a shunt motor, but always in 
the armature circuit. In the differential motor, the 
series winding should be cut out of circuit until the 
motor is started, otherwise the excessive starting cur- 
rent will weaken the field too much. In the cumu- 



j.58 ELECTRICAL TABLES AND DATA 

lative type of motor, the series field adds to the start- 
ing torque. A motor may be tested as to whether it 
is cumulative or differential by starting it with the 
shunt field open. If cumulative it will run in the 
same direction as with the shunt field closed. The 
starting resistances of shunt motors are usually wound 
with fine wire which will overheat and bum out if 
left in circuit too long. Not more than thirty seconds 
should be consumed in manipulating the handle. In 
some cases, however, special apparatus is provided 
which can carry the current indefinitely. If motor 
does not start at once, open switch and look for the 
cause of trouble. 

Power Required to Operate Machinery. — When the 
H. P. needed to operate a given machine is not known 
it may in some cases be calculated from the formula : 

„ p _ Px2>n-xrxn 
"12x33,000xe 

where P =pull in pounds which must be applied at 
periphery of pulley to move it ; r = radius of pulley in 
inches; n- number of revolutions per. minute; e = the 
efficiency of a direct current motor or the product of 
efficiency and power factor in an alternating current 
motor or circuit. 

If the- machinery to be started is equipped with 
heavy flywheels, or possesses considerable inertia of 
any kind, the size of the motor needed is governed by 
the starting requirements which depend largely upon 
the rate of acceleration demanded. In connection 
with other machinery, such as ventilating fans for 
instance, the power required increases faster than the 
speed and can be measured only when the device is 
operating at full speed. For such motors the above 
formula cannot be used and it is necessary to obtain 
data from manufacturers or other users. 



ELECTRICAL TABLES AND DATA 



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160 ELECTRICAL TABLES AND DATA 

LiTT X f* X 'Yh 

In the table below the values of ^ — tttttu^ — 

12x33,000x6 

(e being assumed as of about .75) are given wherever 

the horizontal line pertaining to speed crosses with a 

vertical line pertaining to radius of pulley. 

Care must be exercised in determining P; it must 
not be more than just enough to cause motion, and at 
best can be only an approximation. P may be deter- 
mined by a spring balance, or by a weight and lever. 
If the latter is used and attached to rim of pulley, 
multiply weight by distance from center of pulley 
and divide by radius of pulley. 

Group vs. Individual Drive. — The total H, P. ca- 
pacity of motors for individual drive must be equal 
to the H. P. demands of all the machinery. 

The H. P. capacity for group drive may be con- 
siderably less, because not all of the driven machinery 
is used at the same time. How much of saving there 
is in any given case depends upon circumstances. 
Very often the shafting necessary with group drive 
requires as much additional H. P. capacity as is saved 
by the other consideration above. 

The total H. P. required for group drive can be 
found by the formula: 

H p = (h.p.xf)+s 
e 

where h. p. is the horsepower demanded by the total 
machinery if run all at the same time; / is the load 
factor ; s the H. P. required to drive shafting, and e 
the efficiency of the motor. The large motors used for 
group drive are more efficient at full load than the 
smaller ones, but a group drive motor is seldom run 
at full load. If it is properly chosen it will be over- 
loaded part of the time and inevitably be running 
with no other load than the shafting part of the time. 



ELECTRICAL TABLES AND DATA 161 

The nearer it can be kept running with full load the 
more efficient it will be. The total H. P. required for 
individual drive is equal to the sum of the H. P. of 
all the machines divided by the efficiency. The full 
load efficiency of the small motors is lower, but there 
is never any idle machinery or shafting to be moved, 
and if properly selected the motors may operate at 
full load efficiency most of the time. In most cases 
individual drive is the most economical where a per- 
manent installation is considered, but the cost of 
installation is generally somewhat higher. In addi- 
tion to the above advantages, which can be figured out 
in dollars and cents, the following considerations 
should be of interest and duly noted: With indi- 
vidual drive the fire and life hazard are somewhat 
increased, but the shafting and belting accidents are 
greatly decreased. In connection with low voltage 
(110 or 220) the life hazard is small, and the advan- 
tage is on the side of the individual drive. With 
high voltage group drive is probably safer. With 
individual drive the facilities for speed regulation are 
better and motor troubles cannot throw a whole shop 
out of order. There is no shafting to cause dirt and 
noise and interfere with illumination, and there is 
less vibration in the workroom. Individual drive, 
however, requires somewhat more care and atten- 
tion. 

Where we have the choice of motors of different 
efficiencies we can afford to expend for the motor of 
the better efficiency a sum of money upon which the 
annual interest charge will be equal to the saving in 
the cost of energy effected by the better motor. We 
must, however, select the rate of interest so as to 
cover all depreciation, and if we assume that the 
motor will be a dead loss at the end of the time it is 
to be used, we shall obtain the following rates of 
interest, using a 6 per cent basis: 



B2 ELECTRICAL TABLES AND DATA 

Motor to be used 1 year only, 106 per cent 

2 years, 56 " 

3 vears. 40 " 



3 years, 40 

4 years, 32 

5 years, 27 

6 years, 24 

7 years, 21i 

8 years, 20 

9 years, 18f 



2 



For longer periods of time the interest rate decreases 
slowly and the above will cover all ordinary cases. 

According to the above principles we can determine 
the amount of money we may economically invest in 
order to substitute a motor of higher efficiency for 
another with lower efficiency by the formula, 

~_K.W. xrxkxdxe 
per cent interest 

where C = capital to be invested; K. "W. = the number 
of watts used; r=the rate per K. W. hour; h=the 
number of hours K. W. is used per day; d = the num- 
ber of days per year ; e = the difference in efficiency of 
the two motors; per cent interest = the rate of interest 
governed by the number of years motor is to remain 
in use as given above. 

In the following table it is assumed that the motor 
will be used 300 days per year, and on this basis the 
numbers given represent the capital which could prof- 
itably be invested with K. W., r, and h equal to unity, 
and e and the rate of interest as given in the table. 
To use the table for determining how much can prof- 
itably be invested to substitute a more efficient motor 
in place of a poorer one, it is but necessary to find the 
product of K.W.xrxh, and with this multiply the 
number found where the horizontal line pertaining to 
the difference in efficiency in favor of the better motor 



ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 165 

crosses with the rate of interest applicable to the 
problem. The result will be the sum in dollars and 
cents which can with profit be expended to procure 
the better motor. 

Rule of Tables — Find the difference in efficiency 
between the motors considered and the number of 
years the motor is to be used. Select the number 
found in the longitudinal line where the correspond- 
ing efficiency (given in vertical column at the left) 
crosses with the proper rate of interest (given at top) ; 
multiply this number by the K. W. hours per day, and 
by the rate per K. W. The result will give the amount 
of money which may be invested to procure the motor 
of higher efficiency. If this sum will make up the 
difference in cost, the better motor should be provided. 

Nails. — Use cut nails for driving into brickwork. 



TABLE XXXXIX 
Dimensions of Nails 







Common 


Nails 




Fi 


nishing 1 


Nails 








Diam. 


Approx. 




Diam. 


Approx. 






Nearest 


in 


number 


Nearest 


in 


number 


Size 


Length 


B. &S. 


inches 


per lb. 


B. &S. 


inches 


per lb. 


2d 


1 


13 


%28 


876 


14 


%28 


1351 


3d 


1% 


12 


%4 


568 


13 


%28 


807 


4d 


iy 2 


10 


%4 


316 


13 


9 /(28 


584 


5d 


i% 


10 


Vu 


271 


13 


%28 


500 


6d 


2 


9 


%4 


181 


11 


%2 


309 


7d 


2% 


9 


7 /64 


161 


11 


%2 


238 


8d 


2y 2 


8 


17 /i28 


106 


10 


%4 


189 


9d 


2% 


8 


17 /i28 


96 


10 


7 /64 


172 


lOd 


3 


7 


19 A28 


69 


9 


7 /64 


121 


12d 


3% 


6 


19 /i28 


63 


9 


%4 


113 


16d 


3y 2 


6 


%2 


49 


8 


17 /i28 


90 


20d 


4 


4 


2 %28 


31 


8 


17 /i28 


62 


30d 


4y 2 


4 


2 %28 


24 








40d 


5 


3 


2 %28 


18 








50d 


5% 


2 


31 /i28 


14 








6oa 


6 


2 


3 %28 


11 









166 ELECTRICAL TABLES AND DATA 

National Electrical Code (Abbreviated N.E.C ;. 
— The N. E. C. contains the recommendations of the 
National Fire Protection Association in reference to 
electrical installations. It is revised every two years, 
and its recommendations are generally accepted as 
standard throughout the United States. Most mu- 
nicipalities pattern their regulations after this code, 
but introduce a few variations which local conditions 
seem to warrant. The National Board of Fire Under- 
writers issue ' ' The List of Electrical Fittings. ' ' This 
contains a list of appliances which have been tested 
and are considered safe. Those engaged in electrical 
construction work are advised to keep in touch with 
the N. E. C, the List of Electrical Fittings, and local 
requirements. 

Nernst Lamp. — This lamp is not as much used as 
formerly. It has a high intrinsic brilliancy; requires 
no reflectors; should be hung high. It requires con- 
siderable attention to keep in repair and cannot be 
used in theatres or similar places where quick changes 
are necessary. 

Neutral Wire. — This term describes one of the 
three wires used in connection with the three-wire 
system. Normally this wire carries no current and 
is, therefore, often smaller than either of the outside 
wires. In case an outside fuse blows, it may, however, 
be called upon to carry the full load current. It is 
always fused higher than the outside wires, and often 
is not fused at all. Blowing of the neutral fuse may 
do much damage. Ordinarily this wire is also 
grounded. 

In a star connected polyphase system, the point at 
which all of the wires connect is also spoken of as 
neutral. The fourth wire in a three-phase system 
may also be so termed. 

Non-inductive Load. — A non-inductive load is dis- 
tinguished from an inductive load by the fact that 



ELECTRICAL TABLES AND DATA 167 

the current is in phase with the voltage. Circuits 
supplying only incandescent lamps are very nearly 
non-inductive; arc lamps .and motors make up a 
strongly inductive load. 

Office Lighting. — Desk lights are very common, 
but they are also a nuisance. They cause constant 
annoyance, and increase the fire hazard. 

Inverted lighting is very favorably received in many 
offices and deserves extended trials. The newer high 
efficiency lamps have done much to make it econom- 
ical. Where all employes are constantly at their desks 
there can be no difference of opinion regarding the 
superiority of a good general illumination in every 
respect. Local illumination can appear advisable only 
in such places where most of the desks are occupied 
for a short time per day only. 

Avoid large spreading chandeliers carrying many 
lamps. These often cause a multiplicity of shadows. 
If clusters are used, lamps should be close together. 
Do not run wires in any but the main walls or parti- 
tions; use three-fourths inch conduit so as to have 
plenty of capacity for changes which are always tak- 
ing place. Arrange lighting to harmonize with win- 
dows, so that furniture placed correctly for daylight 
will also fit the artificial illumination. 

Ohm. — The international ohm has been legalized 
in this country and is defined as the resistance which 
a column of mercury of a uniform cross section, at 
the temperature of melting ice, and 106.3 centimeters 
in length, and of a mass of 14.4521 grams, offers to anV 
unvarying electric current. 

TP J? 

Ohms Law.—/—; IxR = E; B=~ 
li i 

Ohmic Loss or Drop. — The loss in e. m. f . or drop 

in p. d. caused by the resistance as distinguished from 
that caused by reactance. 



168 ELECTRICAL TABLES AND DATA 

Overhead Construction. — The timbers most in use 
for poles are : Michigan cedar, Western cedar, chest- 
nut, pine and cypress. Of these the cedars and 
chestnut are the most used. The cedars are easier to 
climb and the taper is greater so that the tops of 
cedar poles are smaller in proportion to the butts than 
chestnut poles. On account of the variable nature of 
the wood and the fact that they soon begin to rot at 
the ground line, which is the point of greatest strain, 
the strength of poles must be calculated with a large 
factor of safety. In the tables following the breaking 
strain of the wood has been taken as 7,000 pounds 
per square inch and a factor of safety of 10 has been 
used. 

Poles are usually designated by their length in feet 
arid diameter at top in inches; thus a pole 40 feet 
long and 8 inches in diameter at top is spoken of as a 
40-8 pole. The standard or most used pole is 35 feet 
long and has a 7-inch top. In swampy places poles 
are often set in concrete. 

Poles should be set with the sweep in the line so 
that the wires may be straight. Use no iron poles 
where lines must be worked on while alive. Set pole 
steps 32 inches apart and stagger them. In cities 
place poles on lot lines. Avoid placing poles near 
lamp posts, hydrants or catch basins. Give corner 
poles a slight rake outward. Use the heaviest poles 
for transformers. Special attention should be given 
to tamping at bottom and top of holes, and the earth 
should be piled up a little around pole to keep water 
from running in. Keep one side of pole free for 
climbing. Double arm all poles subject to unusual 
strains. The lowest cross arm should be at least 18 
feet above ground and 22 feet above railway tracks. 
Allow at least 2 feet between cross arms ; more if pos- 
sible. Insulate guy wires. Make cross arms of uni- 
form length. 



ELECTRICAL TABLES AND DATA 169 

Standard cross arms are rounded on top ; 3J inches 
wide by 4J inches high ; allow- 24 inches between pole 
pins, and at least 12 inches between other pins; this 
distance varies with number of pins, length of span 
and voltage. Junction arms usually have a wider 
spacing between inside pins. The high tension wires 
should be carried on the top arms; secondary wires 
are usually run below them, and the lowest arms are 
left for signal wires if any are to be run on same line. 
There should be a space of about five feet between the 
signal and the lighting and power wires. The lowest 
voltage wires are usually run next to poles; circuit 
wires should be kept together, and neutral of three- 
wire system should be run in center. The fourth wire 
of a three-phase system is also carried next to pole. 

Pole Line Calculations. — The first step in laying 
out a pole line must be to decide upon height of poles 
and maximum span lengths. The next step will be 
to calculate the strains to which poles may be sub- 
ject. The main body of a pole line is subject only to 
wind pressure, and this can be determined by use of 
Table LIL End poles are subject to half of this wind 
pressure and strain from the wires as well. Poles 
from which taps are taken have the full wind pressure 
and strain of wires leading off. Corner poles must be 
considered as subject to 1.41 times the strain on end 
poles. The wire strains upon poles can be found by 
the use of Table LI. The strains upon poles having 
been determined, the proper diameter at ground line 
can be determined by Table LIU. 

When the strains on a pole are found to be greater 
than a pole of desirable diameter can well bear, it 
must be reinforced by guying or bracing. The proper 
diameter of guy cables can be found from Tables 
LV to LVII. If the pole is light compared to the 
strain put upon it, it will be best to provide a guy 
cable to take care of the total strains. 



ELECTRICAL TABLES AND DATA 
TABLE L 



It 


is common practice to string electric power 


wires 


in accordance with the following tabulation, 


which 


gives 


the sa 


g in 


inches : 




Length 








of 






Temperature in Fahrenheit 




span 


20° 


30° 


40° 50° 60° 70° 80° 


90° 


50.. 


. 8 


8 


9 9 10 11 11 


12 


60.. 


. 9 


10 


11 11 12 13 14 


14 


70.. 


. 10 


11 


12 13 14 15 16 


17 


80.. 


. 12 


13 


14 15 16 17 18 


19 


90.. 


. 14 


14 


16 17 18 19 20 


21 


100.. 


. 16 


16 


17 19 20 21 23 


24 


110.. 


. 18 


18 


19 21 22 24 25 


26 


120.. 


. 18 


19 


21 23 24 26 27 


28 


130.. 


. 20 


22 


24 26 28 30 32 


33 


140.. 


. 22 


23 


26 28 30 32 34 


35 


160.. 


. 24 


26 


28 30 32 34 36 


38 



With wires strung according to the above tabula- 
tion each wire at the lowest temperature given will 
cause a strain on poles as given below. To find total 
strain on pole multiply proper number in table below 
by number of wires. By allowing a greater sag the 
strain will be proportionately reduced. 















TABLE LI 
























Bare 


Copper 












Length 


























of 














B. & 


S. Gauge 












'Span 14 


12 


10 


8 


6 


5 


4 


3 2 


1 





00 


000 


0000 


80 


10 


16 


2G 


47 


03 


so 


101 


127 160 


202 


255 


321 


405 


512 


100 


13 


22 


34 


62 


85 


107 


135 


171 215 


272 


343 


432 


545 


688 


120 


15 


24 


39 


70 


95 


120 


151 


190 240 


303 


382 


481 


607 


768 


140 


18 


29 


47 


85 


116 


147 


182 


230 294 


371 


470 


592 


740 


942 


160 


19 


32 


52 


1)4 


120 


160 


202 


254 320 


404 


510 


642 


810 


1024 



Breaking Strains 

B. & S. Gauge 
Hard Drawn — 

14 12 10 8 6 5 4 3 2 1 00 000 0000 
219 343 546 843 1300 1580 1900 2380 2970 3680 4530 5440 6530 8260 
Annealed — 

110 174 277 441 700 884 1050 1323 1670 2100 2650 3310 4270 5320 

Insulation and sleet may easily treble the strains. 



ELECTRICAL TABLES AND DATA 171 

The Maximum wind pressure upon the pole alone 
will range from 125 to 250 lbs., according to length 
and diameter of pole. 

The side strain on a straight pole line (125 ft. 
span ) can be found by use of the table below. Multi- 
ply number of wires on pole by number found under 
size of wire and in proper horizontal line. 

TABLE LII 
Wind Pressure 

B. &S. 14 12 30 8 6 5 4 3 2 1 00 000 0000 
Bare wire.. 8 11 13 19 22 20 29 32 36 40 45 50 55 60 
Insulated ..35 38 41 46 50 53 56 60 65 70 80 90 100 110 

Sleet may easily treble these strains, but sleet seldom exists 
in stormy weather. 

TABLE LILT 

Table showing maximum strains (applied at top) 
to which poles of various heights above ground, and 
of various diameters at ground line, should be 
subject. 



1=3 

O C o 






Height of Poles Above Ground in Feet 


t 3 C 
(SO-'- 

5 60.5 


20 


25 


30 


35 


40 


45 


50 


55 


60 


65 70 


8.. 


147 


118 


98 


84 


74 


66 


58 


53 


49 


46 42 


9.. 


209 


168 


138 


120 


•105 


93 


83 


76 


70 


65 60 


10.. 


286 


228 


191 


164 


143 


127 


115 


104 


95 


88 81 


11.. 


381 


304 


254 


218 


191 


169 


152 


138 


127 


117 109 


12.. 


495 


396 


330 


284 


247 


220 


198 


180 


165 


121 141 


13.. 


624 


500 


416 


356 


312 


278 


250 


226 


208 


192 178 


14.. 


786 


628 


524 


450 


393 


350 


314 


287 


262 


242 224 


15.. 


960 


768 


640 


548 


480 


427 


384 


349 


320 


296 274 


16.. 


1176 


940 


784 


672 


588 


524 


470 


428 


392 


362 336 


17.. 


1407 


1124 


938 


804 


704 


625 


563 


572 


469 


433 402 


18.. 


1658 


1328 


1106 


948 


828 


756 


664 


604 


553 


510 474 


19.. 


1964 


1572 


1310 


1120 


982 


872 


786 


716 


655 


604 562 


20.. 


2288 


1831 


1526 


1284 


H44 


916 


915 


832 


763 


704 652 


21.. 


2665 


2132 


1764 


1524 


1333 


1144 


1066 


968 


885 


820 762 


22.. 


3048 


2440 


2032 


1740 


1524 


1356 


1209 


1108 


1016 


938 870 



ELECTRICAL TABLES AND DATA 







Depth of Setting 










Earth 5 
Bock 4 


5i 


6 6 6| 6i 7 
5 5 5£ 5^ 6 


71 
6i 


8 

7 


81 

7 


9 
9* 



When erected along a curved line it is best to set 
somewhat deeper. 

TABLE LIV 

The following table probably shows the average of 
poles used for general telegraph and telephone 



purposes : 












Butt 


Top 


Wt. 


Butt 


Top 


Wt. 


Length Dia. 


Dia. 


App. 


Length Dia. 


Dia. 


App. 


25... 9 to 10 


6 to 8 


350 


50... 9 to 15 


6 to 8 


1350 


30... 9 to 11 


6 to 8 


450 


55... 16 to 17 


6 to 8 


1700 


35... 9 to 12 


6 to 8 


600 


60... 16 to 18 


6 to 8 


2200 


40... 9 to 13 


6 to 8 


850 


65... 16 to 19 


6 to 8 


2500 


45... 9 to 14 


6 to 8 


1100 


70... 16 to 20 


6 to 8 


3000 



Guys. — Guys should be fastened to pole at point of 
strain and when so fastened the strain upon the guy 
can be found by the formula 



8 = V D^ xp 

where D - horizontal distance at ground of guy from 
pole; H= the height of guy, and P = the pull upon 
the pole. 

TABLE LV 

Table for Calculating Strength of Guys. — To find 
the proper size of wire or wire rope for guying, mul- 
tiply total strain upon pole by number found at 
point where line pertaining to height of guy fastening 
on pole crosses with line pertaining to horizontal dis- 
tance of guy at ground from pole. The product will 
equal the breaking strain of the proper cable or wire 
to be used. The table is calculated for a safety factor 
of 5. 



ELECTRICAL TABLES AND DATA 



Height Horizontal distance in feet from pole to where 
of guy guy or its support leaves ground 

on pole 5 

10 11 

15 16 

20 21 

30 31 

40 40 

50 50 

60 ..... . 60 

70 70 



the 



10 


15 


20 


30 


40 


50 


7.0 


6.2 


5.5 


o.3 


5.2 


5.1 


9.0 


7.0 


6.2 


5.6 


5.3 


5.2 


11 


8.3 


7.0 


6.0 


5.6 


5.5 


16 


11 


9.0 


7.0 


6.3 


5.8 


21 


15 


11 


8.3 


7.0 


6.5 


26 


18 


14 


9.5 


8.0 


7.0 


31 


21 


16 


11 


9.0 


7.6 


36 


24 
TABLE 


18 
LVI 


13 


10 


8.5 



Table Showing Breaking Strain of Cables and 
"Wires. — Standard Steel Strand. American Steel and 
Wire Company. Seven steel galvanized wires twisted 
into a single strand. Galvanized or extra galvanized. 





Approx. 








Weight 


Approx. 


i Galvanized Steel Wire \ 


Dia 


per 


Strength 


Break- 


in 


1000 


in 


A. S. & ing . Nearest 


inches feet 


pounds 


W. G. Dia. Strain B. & S. Dia. 


I 


800 


14000 


12 .106 510 10 .102 


& 


650 


11000 


10 .135 774 8 .128 


* 


510 


8500 


9 .148 942 7 .144 


& 


415 


6500 


8 .162 1170 6 .162 


1 


295 


5000 


6 .192 1770 5 .182 


& 


210 


3800 


5 .207 2079 4 .204 


i 


125 


2300 


4 .222 2433 3 .229 


& 


95 


1800 


The American Steel and Wire 


& 


75 


1400 


gauge is commonly used for 


& 


55 


900 


iron wire. 
TABLE LVII 



"When a pole or mast is held in place by several 
guys equally spaced the figures obtained by the above 
calculation may be divided by the following guy fac- 
tors taken from publication of the American Steel and 
"Wire Company: 



ELECTRICAL TABLES AND DATA 



£ Min. 




Max. 


s value 

bfi „ 

^ factor 


Corresponding 

line of 
action of force 


value 
of guy 
factor 


3 0.866 


30° from 1 guy 


1.000 


4 1.000 

5 1.538 


Opposite 1 guy 
18° from 1 guy 


1.414 
1.618 



6 1.732 30° from 1 guy 



Corresponding 
line of action of force 

Opposite 1 guy or half 

way between two 
Half way between 2 guys 
Opposite 1 guy or half 
way between two 
2.000 Opposite 1 guy 



Telephone Wires. — The tables below give the prac- 
tice of the A. T.' & T. Co. No. 12 hard drawn copper 
wires are strung according to the following table : 







TABLE 


Lvin 










Temp. 
















in 
















Degrees 




Length of Span in 


Feet 








F. 75 


100 


115 130 
Sag in 


150 
Inches 


175 


200 


250 


300 


— 30 1 


2 


21 3| 


41 


6 


8 


14 


22 


— 10 U 


21 


3 4 


5 


7 


9 


16 


251 


+ 10 H 


3 


31 4| 


6 


8 


101 


181 


291 


+ 30 2 


3| 


4 5i 


7 


9| 


12 


21 


33 


+ 60 21 


41 


Si 7 


9 


12 


16 


261 


421 


+ 80 3 


51 


7 8* 


111 


15 


19 


31 


49 


+100 41 


7 


9 11 


14 


18 


221 


36 


55 



The same sag is also allowed for iron wire. 

Messenger Cables. — The standard messenger strands 
used are the following: 

Size of Cable Strength 

No. 22 Gauge No. 19 Gauge of Strand 



100 pair or smaller 
100 to 200 pair 
Larger than 200 pair 



50 pair or smaller 6000 lbs. 

55 to 100 pair 10000 lbs. 

Larger than 100 pair 16000 lbs. 



ELECTRICAL TABLES AND DATA 175 

The above strands are about equivalent to f 7 ^? t% 
and f inch diameters of good quality steel and used 
for spans not exceeding 200 feet. 

The sag allowed is the following : 



Sag in inches 
Sag in when not more than 
inches for 50 pair No. 22 gauge 



in in feet 


heavy cables 


wire will 1 


80 


16 


10 


90 


20 


12 


100 


22 


16 


110 


26 


18 


120 


30 


20 


130 


34 


22 


140 


40 


26 


150 


44 


30 


175 


62 


42 


200 


82 


58 



Panel Boards. — The panel board is a small switch- 
board, but circuits supplying more than 660 watts 
are seldom fed through it. Those described in the 
following figures and tables are designed for 660-watt 
branch circuits. Main bars have a capacity of 6 
amperes per branch circuit at 110 volts, but only 
3 amperes if designed for 220 volts. The figures in 
the tables are those furnished by the Cuthbert Electric 
Mfg. Co. Wherever the depth of cabinet required is 
the same for all numbers of circuits, it has been given 
in the fourth column from the left. In other cases 
the special designations at each height will serve as a 
guide. Where no special mark is placed and no 
depth given, the required depth is 3J inches. When 
ordering boxes, see points to be noted under 
Cabinets. 



ELECTRICAL TABLES AND DATA 



Type 'A-9» 





Figure 12. — Types of Panel Boards. 



cap 
cap 
Kae 

crap 
I 


E3i 
°3 

23! 

"31 
23 



nasn 


c^ap = 


= 3 


KaE: 


'"31 


CS|§ = 


= 31 


g # 


p 


.-31 


1 1 


1 










C2 




s r rj 





3 


S^3 

IP 




Figure 13. — Types of Panel Boards. 



ELECTRICAL TABLES AND DATA 



177 




- - 




:•:: 


■ :: ■:: 


:*-:■.;. 


:■=.::- 


::j: 


US Si 


: :&. 


i e i 





i 


I 1 








■ G •■■■ O ■ 

:8 ' : 

■ G *' ©=■ 



8 5 8 



Figure 14. — Types of Panel Boards. 




8 


8 








1 5 


&2 

1 






Type'E.5' Type'E-6' Type 'F-1' Type 'F-2' 

Figure 15. — Types of Panel Boards. 






! 1 1 







I 3 3 





Type 'F-3* Type 'P-4' Type 'F-5' Type 'F-6' 

Figure 16. — Types of Panel Boards. 



© 
too 

03 . 
© © 



ELECTRICAL TABLES AND DATA 

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ELECTRICAL TABLES AND DATA 



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180 ELECTRICAL TABLES AND DATA 

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ELECTRICAL TABLES AND DATA 181 

Plans. — Except in the ease of large office build- 
ings, hotels, street lighting, and other large under- 
takings, detailed plans cannot show much more than 
location of outlets and most of the information is 
gathered from specifications. In large installations, 
it is customary to designate sizes of conduit as well as 
the wires. In making the installation according to 
such plans the work is often subdivided, separate 
plans being given to different workmen or groups of 
workmen. If each group is allowed to finish its par- 
ticular installation a very reliable check on the labor 
performed by each man or group is obtained. 

Small plans are usually drawn to a scale of J inch, 
per foot ; for large plans the scale is often -J inch, or 
even less. Details are drawn to a larger scale and 
sometimes even full size. 

Power. — This term expresses merely the rate of 
doing work. In order to obtain the quantity, it must 
be multiplied by time. Power is measured in watts 
and is usually expressed in watt hours, kilowatt hours, 
or horsepower hours, but any other length of time may 
be chosen. 

Preservation of Wood. — This is effected by impreg- 
nating the timber with some sort of poison which 
destroys the fungi and deprives them of food. Creo- 
sote is the most used, and there are various patented 
substances of a similar nature. The more thoroughly 
dried the timber is at time of application, the more 
it will absorb. Ordinarily the preservative is applied 
with a brush, but it is also applied under pressure, the 
whole pole or tie being submerged in a tank full of 
the impregnating material, to which pressure can be 
applied. 

Printing. — Printing presses are usually equipped 
with reversible and variable speed motors. For the 
larger sizes several motors are used. All of these are 
preferably fitted with remote control switches which 



182 ELECTRICAL TABLES AND DATA 

enable the operator to govern the press from various 
points on and about it. Time is a very important 
consideration about large presses and the very best 
illumination should be supplied. On many presses 
from 10 to 20 lights are permanently installed so as to 
be ready at a moment's notice and obviate the neces- 
sity of using portable lamps. Such lights also assist 
in watching the mechanism while at work. Flexible 
conduit is serviceable, but it should be lead covered to 
guard against machine oil, which dissolves rubber. 

Composing Rooms. — A good general illumination is 
advisable in composing rooms, but there must be local 
illumination with it in certain places. In some com- 
posing rooms the work is of such a nature that it is 
advisable to fit each stand with a foot or arm switch 
by which a compositor can turn the light on or off 
without using his hands. 

Pumping. — One cubic foot of water weighs ap- 
proximately 62.5 pounds and contains about 7.5 gal- 
lons. One gallon weighs 8.33 pounds and contains 
231 cubic inches. If the head of a column of water is 
expressed in feet and the pressure at the foot of the 
column in pounds per square inch, then 

Head = 2.31 x pressure 

Pressure = head ~ 2.31, which equals 0.434 x head, 
and this is independent of size of column. 

The H. P. required to deliver a certain quantity of 
water to a certain height is directly proportional to 
the product of the two if the so-called "friction head" 
is added to the actual height of lift. The friction 
head for various sizes of pipe and rate of flow through 
them is given in Table LXII. This friction head 
varies with the square of the velocity of the liquid, 
with the distance it flows, and with the conditions 
affecting its freedom of movement. Elbows, bends, 
burs, etc., increase it. The enormous losses in pres- 



ELECTRICAL TABLES AND DATA 183 

sure which take place when a small pipe is used for 
the delivery of a large amount of water can be seen 
from the table. The efficiency of centrifugal pumps 
is sometimes as low as 35 per cent, and that of rotary 
and plunger pumps ranges from 60 to 80. 

Table LXII shows the resultant net efficiency of 
motors and pumps of various efficiencies working 
together. 

From Table LXII we can take the number of cubic 
feet, pounds and gallons which one horsepower will 
lift to a height of one foot, the machinery having a 
net efficiency as given. 

Rule for Determining Horsepower Needed. — Add 
to the actual head in feet the friction head as found 
in Table LXII and multiply this by the number of 
cu. ft., lbs. or gals., as the case may be. Next divide 
this sum by the number found in same table under the 
efficiency of the combination to be used: combined 
motor and pump efficiency. 

Table showing number of cu. ft., lbs., or gals, which 
can be raised 1 foot per minute by 1 H. P. at effi- 
ciencies given. 



TABLE LXII 

Combined Motor and Pump Efficiency. 

64 60 56 52 48 46 43 40 

Cu.Ft. 338 316 296 275 253 243 227 211 

Lbs.. 21,120 19,800 18,480 17,160 15,840 15,180 14,190 13,200 

Gals.. 2,535 2,370 2,220 2,062 1,897 1,822 1,702 1,582 

Combined Motor and Pump Efficiency. 

38 36 34 32 30 28 26 24 

Cu.Ft. 200 190 180 169 158 148 137 127 

Lbs.. 12,500 11,880 11,220 10,560 9,900 9,240 8,580 7,920 

Gals. 1,500 1,425 1,350 1,267 1,185 1,110 1,027 952 



ELECTRICAL TABLES AND DATA 



TABLE LXII— Continued 

Friction head per hundred feet of pipe of inside 
diameters given. Condensed from Westinghouse 
Electric & Mfg. Co. table. 

Inside Diameters of Pipes. 



Cu.Ft. Lbs. 


Gals. 


%" 


1" 


iy 4 " 


iy 2 " 


2" 


2y 2 » 3" 


0.6 


37 


5 


7.59 


1.93 


0.71 


0.27 






1.1 


75 


10 


29.9 


10.26 


2.41 


1.08 






1.6 


112 


15 


66.01 


16.05 


5.47 


2.23 






2.4 


150 


20 


115.92 


28.29 


9.36 


3.81 






3.0 


187 


25 




43.70 


14.72 


5.02 


1.18 




3.4 


225 


30 




63.25 


21.04 


8.62 


2.09 




4.2 


263 


35 




85.10 


28.52 


11.61 


2.76 




4.8 


300 


40 




110.40 


37.03 


14.99 


3.68 


1.19 


5.2 


338 


45 






46.46 


18.74 


4.60 


1.49 


6.0 


375 


50 






57.27 


23.00 


5.61 


1.86 0.80 


9.0 


562 


75 






129.09 


51.52 


12.23 


4.14 1.70 


12.0 


750 


100 








89.70 


21.75 


7.36 3.01 


15.0 


937 


125 










34.27 


11.24 4.57 


18.0 


1,125 


150 










48.76 


16.10 6.55 


21.0 


1,312 


175 










64.63 


21.75 8.85 


24.0 


1,500 


200 










86.25 


28.68 11.54 


30.0 


1,875 


250 












45.21 17.84 


36.0 


2,250 


300 












64.53 25.76 


42.0 


2,625 


350 












34.96 


48.0 


3,000 


400 












44.85 


60.0 


3,375 


450 












57.50 


75.0 


3,750 


500 












70.84 



ELECTRICAL TABLES AND DATA 185 

Table for determining com- Theoretical and practical 

bined efficiency of pump and suction limit, 
motor. 

TABLE LXII— Continued 



Motor 
Efficiency 




Puni] 


:> Efficiency 


Altitud'e Theoretical Practical 
Sea level 33.95 25 


75 


65 


50 


45 


40 


35 


1,320 ft. above 


32.38 


24 


70 52 


46 


35 


32 


28 


24 


2,640 ft. above 


30.79 


23 


75 56 


48 


38 


34 


30 


26 


3,960 ft. above 


29.24 


21 


80 60 


52 


40 


36 


32 


28 


5,280 ft. above 


27.76 


20 


85 64 


56 


43 


38 


34 


30 


10,560 ft. above 


22.82 


17 



Reactive Coils. — This term describes coils intro- 
duced- into a circuit to produce a certain reactance. 
They are also known as reactors. They are used to* 
limit short-circuiting currents. Reactors are usually 
designed for a high temperature rise, and should be 
treated as sources of heat. When used in connection 
with lightning arresters they are often spoken of as 
" choke coils." 

Rectifiers. — The mercury-arc rectifier is the one 
most used for arc lamp operation and is very common 
in motion picture theaters. Other types are the elec- 
trolytic and rotary. The mercury-arc type is also 
much used for storage battery work in connection 
with automobile charging. It is usually fed through 
autotransformers, but sometimes through constant 
current transformers, and then delivers a constant 
current. Most rectifiers are operated on single-phase 
circuits, but they can be arranged for two-phase and 
three-phase circuits and operate more advantageously. 
They may also be operated in parallel. Rectifiers de- 
signed for 40 to 50 amperes usually have glass tubes, 
but if larger capacities are required, the tubes are 
metallic. The power factor is ordinarily about 0.90. 
The drop in voltage is always about the same, hence 



186 ELECTRICAL TABLES AND DATA 

the lower the voltage the lower the efficiency. The 
average efficiency is about 75 or 80 per cent. If the 
vacuum is good, shaking the tube will cause a metallic 
sound ; if tube is dirty on inside, the vacuum is usually 
poor. 

Reciprocals of Numbers. — The reciprocal of any 
number is equal to 1 divided by that number. The 
reciprocal gives by multiplication what the number 
would give by division, and vice versa. The prin- 
ciple involved is made use of in many formulae and 
is much used to facilitate calculations. The recipro- 
cals have been given only for whole numbers and up 
to the number 100. The reciprocal of any number 
larger or smaller may, however, easily be found by 
adding a decimal point to the reciprocal for each num- 
ber added to its integer or subtracting one for each 
integer taken from the whole number. The larger 
the number, the more decimal places the reciprocal 
will contain. The smaller the number, the greater 
wall be its reciprocal. 



Thus the reciprocal of 7.3 


0.13698 


73 


0.013698 


730 


0.0013698 


7300 


0.00013698 


0.73 


1.3698 


0.073 


13.698 


0.0073 


136.98 



To find the reciprocal of a number trace along until 
this number is found. Thus the reciprocal of 21.7 
is 0.04608. 

To find the number pertaining to any reciprocal 
find the reciprocal and take the number. Thus the 
whole number of which 0.2710 is the reciprocal is 36.9. 



ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 191 

Reflectors. — Perfect prismatic glass makes the 
very best reflector. The following table gives approxi- 
mately the percentage of light reflected by. various 
materials : 

TABLE LXIV 

Per Cent 
Light 

Kefiected 

Well polished silver 92 

Silvered mirror 70 to 90 

Highly polished brass 70 to 85 

Mirror backed with amalgam .• 70 

Well polished copper 60 to 70 

Well polished steel 60 

Burnished copper 40 to 50- 

Chrome yellow paper 60 

Orange paper 50 

Yellow paper or painted wall 40 

Pink paper 35 

Blue wall paper 25 

Emerald green paper 1& 

Dark brown paper 13- 

Vermilion paper 1& 

Bluish green paper 12 

Cobalt blue paper 12 

Deep chocolate colored paper 4 

Black cloth 1.2 

Black velvet 0.4 

Refrigeration. — Refrigeration by machinery is 
much more reliable, effective and cleanly than that 
produced by the use of ice. Electric power compares 
favorably with steam power in large installations, but 
more especially so in the smaller plants. Its main 
advantages are : lower first cost, less space required ; 
less attendance and operation ; can be made automatic. 
For direct current, compound- wound motors are pref- 
erable, and where variable speed is desired, the speed 
control should be by means of field regulation. For 
alternating current, the squirrel cage type of arma- 



192 ' ELECTRICAL TABLES AND DATA 

ture may be used, but if speed control is desired, a 
wound armature should be provided. The latter is 
much preferable for automatic control. The horse- 
power required for refrigeration can be determined 
by means of the curves in Figure 17, due to Westing- 
house Electric & Mfg. Co. The upper curve is for 
compressors of 50 H. P. and smaller; the lower curve 




Figure 17. 



for larger machines. For example: a 30-ton com- 
pressor requires a 52 H.P. motor; a 300-ton com- 
pressor requires a 470 H.P. motor. When the ice- 
making capacity of compressor is given, the motor 
H.P. required will in general be about double the 
figure given in the curve. 

Refrigerators. — All refrigerators are at times very 
damp. As long as they are kept cold, ice forms, and 
as soon as they are empty the ice melts and all parts 
become wet. No very bright illumination is required, 
and in many of them workmen are required to s^et 



ELECTRICAL TABLES AND DATA 193 

along with lanterns. Weatherproof construction is 
preferable to conduit in all places except where heavy 
coatings of ice form on the wires. This frost is scraped 
off from time to time, and open wires are likely to be 
torn loose. Porcelain sockets break easily and should 
not be used. Circuits should not enter or leave too 
close to entrances; the meeting of the cold and warm 
air at such places cause the deposit of much moisture. 
Lamps are usually placed only in runways, and in 
large refrigerators the circuits are apt to be long. In 
some of the large refrigerators watchmen are regu- 
larly making rounds ; in such places three-way switches 
at doors are useful. Keep cut-outs and switches out- 
side of damp rooms and avoid the use of the common 
fiber-lined brass shell socket. 

Residence Wiring. — As a general rule a total 
wattage capacity. of about \ watt per sq. ft. should 
be provided for the whole building, including cellar 
and attic. If these latter are not to be illuminated, 1 
watt per sq. ft. will be ample for the balance of 
house. The best place for service switch and meters 
is in the basement. Select a location easily accessible 
to meter readers. If not too much economy is neces- 
sary, let two circuits enter each room that contains 
more than one outlet. Place all switches at doors 
where room is most likely to be entered, and if there 
are two entrances two-way switches will be a great 
convenience. In some elaborate residences circuits 
are sometimes so arranged that lights in all rooms 
may be thrown on by a master switch, even if turned 
off in rooms. This is useful as burglar protection 
and also in case of fires. A measure of protection 
against intruders can be obtained by placing lights 
above doors so that an intruder must show himself 
in the light before he can enter a room. The bright 
light will prevent him from seeing what is inside 
the door. 



194 ELECTRICAL TABLES AND DATA 

Attics. — No part of residence requires light more 
than the attic. The use of matches is exceedingly 
dangerous in such places. Run wires where they will 
not be molested. 

Bathroom. — A center light in a bathroom is an 
abomination. Place a light at each side of shaving 
mirror if practicable, but locate them so that person 
in tub cannot reach socket. An outlet for heater will 
be a great convenience. If possible place or shade 
lamps so they will not cast shadows of persons on 
window. Place a switch at door. If expense is no 
object, inverted lighting will be very useful. 

Basement. — The wiring of the basement depends 
upon the use to which it may be put. Two or three- 
way switches, one at each entrance, will be very con- 
venient. Plenty of light will be an inducement for 
servants to keep basement cleaner than the average. 
Provisions should be made for motors to operate ice 
cream freezers, washing machines, mangels, or vacuum 
cleaning motors. It is much preferable to place the 
motor for this purpose in the basement rather than to 
bother with portable machines. Fan motor outlets 
will assist in drying clothes. If part of basement is 
used as laundry and likely to be damp, use weather- 
proof construction and avoid placing sockets where 
one standing on wet floor will be likely to touch them. 
Provide outlet for flatiron. 

Bedrooms. — A center fixture should never be in- 
stalled in a bedroom unless it is intended also as a sort 
of living room. Lights should be arranged to suit 
the various positions in which a bed can advantage- 
ously be placed, and so that one can use the light for 
reading in bed or make easy connections for heating 
pads. Special outlets along baseboard for flatiroif 
heaters, sewing machine motors, etc., will be found 
very useful. One light on each side of dresser mirror 
is a great convenience. Avoid placing lights so that 



ELECTRICAL TABLES AND DATA 195 

they will cast shadows of occupants on windows. For 
protection against burglars, a switch by which lights 
in other rooms may be turned on is very effectual. 
See "Modern Wiring Diagrams and Descriptions' ' 
for circuits. Such a switch might be placed in each 
bedroom. Inverted lighting is very useful if only one 
light can be installed and if ceilings are light enough. 
Cellars. — A cellar is usually damp, and weather- 
proof construction should be used. Keep switch out- 
side at door. 

Closets. — The use of matches in closets is very dan- 
gerous and will be entirely eliminated by good illum- 
ination. Place a light at ceiling and control by switch 
if closet is small. In large closets a pendant light may 
be advisable, but there is usually too much chance of 
clothing coming in contact with it and the cord. 

Dining Rooms. — Beam lighting is used to some ex- 
tent in dining rooms. Special illumination of buffet 
and china closet is also often practiced. Small lamps 
are used for the latter and should be located to show 
off cut glass, etc., to the best advantage. It is well 
to study the effect of such lights carefully before 
finally locating them. To show off silverware, fine 
table linen, etc., to the best advantage it is advisable 
to concentrate a strong light upon the table and 
leave balance of room somewhat dark. Side outlets 
for fan motors, and floor sockets for chafing dishes, 
are very useful. The low hanging fixtures often seen 
in dining rooms should not be recommended. They 
will soon become obnoxious. 

Halls. — Halls ordinarily require only a perfunc- 
tory illumination unless a showy appearance is de- 
sired. These lights are often combined with stair 
lights and fitted with two or three-way switches. 
Place switch for hall light close to the door. 

Ice Boxes or Chambers. — A light placed opposite 
door will be very useful. 



196 ELECTRICAL TABLES AND DATA 

Kitchen. — If kitchen walls are of light color, a cen- 
ter light will give good illumination. With dark col- 
ored walls a light should be placed over sink and near 
range, but a little to one side, so as to avoid the cook- 
ing fumes as much as possible. A small motor to 
drive steam out will be of great use. Ozonators to 
destroy odors will also be much appreciated. As 
ironing is often done in the kitchen, an outlet for 
irons should always be provided. If electric cooking 
is indulged in this must be provided for. 

Laundry. — There should be a light directly over 
wash tubs and another arranged to be directly over 
ironing board. If clothes are dried in laundry a fan 
or ventilating motor will be of great service. Pro- 
visions should be made for washing machine motors, 
mangels and flatiron. Locate sockets so persons will 
not be likely to touch them while standing on wet 
floor. 

Lavatory. — One light controlled by door-switch is 
very useful here. 

Library. — Inverted lighting of sufficient c.p. to 
allow the reading of titles of books in cases is the best 
means of illumination here. In addition to this there 
should be outlets for reading lamps and brackets con- 
veniently located on walls to give a brighter light for 
those that need it. A direct light with strong reflector 
under inverted light is useful for reading purposes. 

Nursery. — The lighting of the nursery should be 
ample, but precautions should be taken to guard 
against the possibility of outlets being short circuited 
by children. Avoid placing sockets within easy reach. 
Electric toys should be confined to battery current, 
or a low- voltage transformer, to which children have 
no access, might be used. The lighting voltage is too 
dangerous for them. Control all lights by switches 
and keep them high. 



ELECTRICAL TABLES AND DATA 197 

Pantry. — Provide bright illumination to show up 
dust and dirt and induce cleanliness. 

Parlor. — The illumination of the parlor is usually 
effected by means of quite elaborate chandeliers. Out- 
lets for piano and reading lamps should be provided. 
The center light does not illuminate pictures very 
well, and for this reason inverted lighting is often 
useful. Really good pictures, however, deserve spe- 
cial illumination. 

Porch. — A light should be arranged close to main 
entrance and so located as to reveal features of per- 
sons applying for admission without making the 
party inside of house visible. The light should be 
controlled by a switch inside and should be out of 
reach from the outside. If porch is to be enclosed, 
other outlets for lamps or fan motors will be useful, 
but they should be arranged at ceiling so as to avoid 
moisture. Use no fiber lined sockets outside. 

Resuscitation from Electric Shock. — Rules recom- 
mended by commission on resuscitation from electric 
shock, representing The American Medical Associa- 
tion, The National Electric Light Association, The 
American Institute of Electrical Engineers. Issued 
and copyrighted by National Electric Light Associa- 
tion. Reprinted by permission. 

Follow these instructions even if victim appears 
dead. 

/. Immediately Break the Circuit. — With a single 
quick motion, free the victim from the current. Use 
any dry non-conductor (clothing, rope, board) to 
move either the victim or the wire. Beware of using 
metal or any moist material. While freeing the vic- 
tim from the live conductor have every effort also 
made to shut off the current quickly. 

II. Instantly Attend to the Victim' 's Breathing. — 
(1) As soon as the victim is clear of the conductor, 
rapidly feel with your finger in his mouth and throat 



198 ELECTRICAL TABLES AND DATA 

and remove any foreign body (tobacco, false teeth, 
etc.). Then begin artificial respiration at once. Do 
not stop to loosen the victim's clothing now; every 
moment of delay is serious. Proceed as follows: 

a. Lay the subject on his belly, with arms extended 
as straightforward as possible and with face to one 
side, so that nose and mouth are free for breathing. 




Figure 18. Inspiration — Pressure Off. 



See Figure 18. Let an assistant draw forward the 
subject's tongue. 

b. Kneel straddling the subject's thighs and facing 
his head; rest the palms of your hands on the loins 
(on the muscles of the small of the back), with fingers 
spread over the lowest ribs, as in Figure 18. 

c. With arms held straight, swing forward slowly 
so that the weight of your body is gradually, but not 
violently, brought to bear upon the subject. See Fig- 
ure 19. This act should take from two to three 
seconds. 

Immediately swing backward so as to remove the 



ELECTRICAL TABLES AND DATA 199 

pressure, thus returning to the position shown in 
Figure 18. 

d. Repeat deliberately twelve to fifteen times a min- 
ute the swinging forward and back — a complete res- 
piration in four or five seconds. 

e. As soon as this artificial respiration has been 
started, and while it is being continued, an assistant 




Figure 19. Expiration — Pressure On. 



should loosen any tight clothing about the subject's 
neck, chest or waist. 

(2) Continue the artificial respiration (if neces- 
sary, at least an hour), without interruption, until 
natural breathing is restored, or until a physician 
arrives. If natural breathing stops after being re- 
stored, use artificial respiration again. 

(3) Do not give any liquid by month until the sub- 
ject is fully conscious. 

(4) Give the subject fresh air, but keep him warm. 
777. Send for Nearest Doctor as Soon as Accident 

Is Discovered. 



.200 ELECTRICAL TABLES AND DATA 

Ropes. — 

TABLE LXV 

iStandard Iron Hoisting Eope, 6 Strands — 19 Wires to the 
Strand — 1 Hemp Eope. American Steel & Wire Co. 



1>R 









OS M 

S.S 


o.2 


g-SR 

<fe.S 


2| 


8| 


11.95 


n 


71 


9.85 


n 


7J 


8.00 


2 


6i 


6.30 


u 


5| 


5.55 


if 


51 


4.85 


it 


5 


4.15 


li 


4| 


3.55 


if 


4J 


3.00 


li 


4 


2.45 


li 


3| 


2.00 


i 


3 


1.58 


I 


2| 


1.20 


1 


2i 


0.89 


f 


2 


0.62 


ft 


If 


0.50 


i 


li 


0.39 


ft 


li 


0.30 


1 


1* 


0.22 


ft 


1 


0.15 


i 


I 


0.10 



CD -P 
q_, & R 

o O O GQ g 



§R^ .§2^ £^ 

ass s§ Hi 

<30QO RR* fiP<^ 

111.0 22.2 17 

92.0 18.4 15 

72.0 14.4 14 

55.0 11.0 12 

50.0 10.0 . 12 

44.0 8.8 11 
38.0 7.6 ' 10 

33.0 6.6 9 

28.0 5.6 8.5 

22.8 4.56 7.5 

18.6 3.72 7.0 

14.5 2.90 6.0 

11.8 2.36 5.5 

8.5 1.70 4.5 

6.0 1.20 4.0 
4.7 0.94 3.5 
3.9 0.78 3.0 
2.9 0.58 2.75 

2.4 0.48 2.25 

1.5 0.30 2.00 

1.1 0.22 1.50 



For better grades of rope smaller sheaves are 
advised. 



ELECTRICAL TABLES AND DATA 
Manila Eope. 



CD «H 



CD 

a 
S 


S 
5 


1 d 

.5 § 

Poq 


O Q 


a 

s 


S 

5 


2 &D - 

Is 

in *"* 
p02 


O CD 


\ 


i+ 


2,000 


0.09 


If 


4* 


13,500 


0.65 


8 


2 


3,250 


0.14 


H 


4| 


15,000 


0.77 


1 


21 


4,000 


0.20 


If 


• 41 


18,200 


0.90 


& 


24 


6,000 


0.27 


If 


5i 


21,700 


1.05 


1 


3 


7,000 


0.35 


2 


6 


25,000 


1.40 


1* 


31 


9,300 


0.45 


2i 


61 


32,000 


1.75 


li 


31 


10,000 


0.55 


2* 


74 


40,000 


2.15 



Splicing of Manila Rope. — The successive opera- 
tions for making a common or English splice in a 
If -inch 4-strand rope is as follows: 

1. Tie a piece of twine, 9 and 10, A, Figure 20, 
around the rope to be spliced, about six feet from 
each end. Then unlay the strands of each end back to 
the twine. 

2. Put the ropes together and twist each corre- 
sponding pair of strands loosely, to keep them from 
being tangled, as shown at A. 

3. The twine 10 is now cut, and the strand 8 unlaid 
and stran^ 7 carefully laid in its place for a distance 
of four and a half feet from the junction. 

4. The strand 6 is next unlaid about one and a half 
feet and strand 5 laid in its place. 

5. The ends of the cores are now cut off so they 
just meet. 

6. Unlay strand 1 four and a half feet, laying 
strand 2 in its place. 

7. Unlay strand 3 one and a half feet, laying in 
strand 4. 



202 ELECTRICAL TABLES AND DATA 

8. Cut all the strands off to a length of about 
twenty inches, for convenience in manipulation. The 
rope now assumes the form shown in B, with the 
meeting point of the strands three feet apart. 

Each pair of strands is now successively subjected 
to the following operations: 




Figure 20. — Method of Splicing Ropes. - 



9. From the point of meeting of the strands 8 and 
7 unlay each one three turns; split both the strand 8 
and the strand 7 in halves, as far back as they are 
now unlaid, and the end of each half strand 
"whipped" with a small piece of twine. 

10. The half of the strand 7 is now laid in three 
turns, and the half of 8 also laid in three turns. The 
half strands now meet and are tied in a simple 



ELECTRICAL TABLES AND DATA 203 

knot 11, C, making the rope at this point its original 
size. 

11. The rope is now opened with a marlinspike, 
and the half strand of 7 worked around the half 




Figure 21. — Methods of Tieing Knots. 



strand of 8 by passing the end of the half strand 
through the rope, as shown, drawn taut, and again 
worked around this half strand until it reaches the 
half strand 13 that was not laid in. This half strand 
13 is now split, and the half strand 7 drawn through 
the opening thus made, and then tucked under the 
two adjacent strands, as shown in D. 



204 ELECTRICAL TABLES AND DATA 

12. The other half of the strand 8 is now wound 
around the other half strand 7 in the same way. 
After each pair of strands has been treated in this 
manner, the ends are cut off at 12, leaving them 
about four inches long. After a few days' wear they 
will draw into the body of the rope or wear off, so 
that the locality of the splice can scarcely be detected. 

Figure 21 shows specimens of knots frequently 
used. 

A, Bowline; B, Stevedore knot; C, Eeef knot; D. Weavers 
knot; E, Boat knot; F, Half hitch; G, Timber hitch; H, Clove 
hitch ; /, Timber and half hitch ; J, Blackwall hitch ; K, Common 
noose; L, Fishermen's bend; M, Common knot; N, Turks head. 

Saloons. — In small saloons not much illumination 
is required. Where there is any pretense of impor- 
tance, however, there is always some back-bar lighting, 
and this may often furnish the whole illumination. 
Special outlets for cash registers and hot water heat- 
ers should be provided. Nearly every saloon sooner 
or later provides a beer pump. In pretentious saloons 
a very elaborate illumination is often striven for. 
In case wine rooms, or other private places fitted with 
glass partitions, are to be illuminated the lights should 
be so placed that they will not cast shadows of occu- 
pants on glass. 

Schools. — In large cities schools are often classed 
as assembly halls and special rules for wiring are 
made. There should be emergency lighting. A stere- 
opticon outlet is a common requirement. 

Screws. — Formulae for wood screws. N = number; 
D = diameter. 

D={Nx 0.01325) +0.056 
D- 0.056 



N=- 



0.01325 



ELECTRICAL TABLES AND DATA 205 

TABLE LXVI 

Dimensions of Iron Screws (Approximate). 

Trade Diameter Nearest Greatest Length 

Number in Fractions B. & S. Gauge Obtainable 

%28 IS % 

1 % 28 14 y 2 

2 %i 12 y s 

3 % 2 11 1% 

4 %4 9 iy 2 

5 % 2 8 2% 

6 1^28 7 3 

7 i% 28 7 3 

8 % 2 6 4 

9 n/64 5 4 

10 i% 4 5 4 

11 i3/ 64 4 4 

12 27/ 128 4 6 

13 2% 3 6 



14 i% 4 3 6 

15 % 2 6 

16 1% 4 2 6 

17 % 2 1 6 

18 i% 4 1 6 

Service Entrance.— The service wires should be 
protected by fuses as close as possible to where they 
enter the building. There should be a service switch, 
and it and the fuses should be accessible. 

Shelving". — To illuminate shelving properly is a 
troublesome matter. Portable lamps are essential, 
but these introduce an appreciable fire hazard. It is 
best to suspend lamps from ceiling by reinforced cord, 
and fit each lamp with a substantial guard. It is 
usually necessary to have good light close to the floor, 
but this can be had by keeping lamps about 6J feet 
above floor. If shelves are deep and contain dark- 



206 ELECTRICAL TABLES AND DATA 

colored materials carrying indistinct numbers, attach- 
ments to these cords will often be necessary. Where 
lights are not constantly in use, three-way ceiling; 
switches will be very useful and economical. Provide 
each group of lamps commonly used together with its 
own switch. 

Show "Windows. — In the best form of show-window 
lighting the lamps are always entirely hidden. Very 
brilliant effects are often striven for and the gas- 
filled mazda lamp is in great favor. Where there is 
bright illumination on the street in front, even greater 
illumination is required within. The object is, not 
only to make things visible, but to attract attention, 
and for this purpose the very brightest and whitest 
light is necessary. Most show windows are lighted 
from the top by reflectors, but in some cases an illum- 
ination from the bottom up must also be provided. In 
some cases the object is to show the lights and call 
attention to the fact that they are there. For this 
purpose small lamps, well frosted, are preferable. If 
they are too bright they will blind people to the ob- 
jects in window. In some cases 32 c.p. lamps have 
been thickly studded over the whole ceiling of window. 
Time switches are much used for show-window light- 
ing and enable one to keep his windows illuminated 
fcr advertising purposes after the store is closed. 
Fan motor outlets are very useful for winter to keep 
windows clear of frost. Place no wires near glass 
where water is liable to run down. 

Signs, Electric. — Signs should be wired with the 
two sides independent so as to enable flasher to be 
used. Small lamps of low intrinsic brilliancy are 
preferable. Letters should be glossy white and kept 
clean. The following table gives dimensions and 
numbers of sockets of stock letters made by the Fed- 
eral Electric Co. of Chicago, which may serve as a 
general guide to present practice. 



ELECTRICAL TABLES AND DATA 
TABLE LXVII 





10 Inch 
Letters 


14 Inch 

Letters 


16 Inch 

Letters 

4 Lamp High 


16 Inch 

Letters 

5 Lamp High 


24 Inch 

Letters 










5 
■a 


M 


-3 


-2 


si 




si 


























m 


£ 


p 


* 


o 


£ 





% 


. O 
Ul 


* 


A 


8 


10 


8 


12% 


8 


154 


10 


15% 


11 


21 


B 


JO 


10 


10 


124 


11 


154 


13 


15% 


13 


21 


C 


7 


10 


7 


124 


7 


154 


8 


154 


8 


21 


D 


8 


10 


8 


124 


9 


154 


11 


15% 


11 


21 


E 


9 


10 


9 


124 


9 


154 


10 


15% 


13 


21 


F 


7 


10 


7 


124 


7 


154 


8 


15% 


10 


21 


G 


8 


10 


8 


124 


8 


154 


9 


15% 


11 


21 


II 


9 


10 


9 


124 


9 


154 


11 


15% 


12 


2L 


I 


4 


5% 


4 


6 


4 


8 


5 


8 


5 


9 


J 


6 


10 


6 


3 24 


6 


154 


7 


15% 


7 


21 


K 


8 


10 


8 


124 


9 


154 


11 


15% 


11 


21 


L 


6 


10 


6 


12 1 ., 


6 


154 


7 


15% 


8 


21 


M 


13 


1214 


13 


154 


13 


194 


15 


19% 


17 


25 


N 


10 


10 


10 


15 1 ; 


10 


154 


13 


15% 


13 


21 





8 


10 


8 


154 


9 


154 


10 


15% 


10 


21 


P 


8 


10 


8 


151.; 


8 


154 


10 


154 


10 


21 


Q 


9 


10 


10 


15>< 


9 


154 


10 


15% 


11 


21 


R 


10 


10 


10 


154 


10 


154 


12 


15% 


12 


21 


S 


8 


10 


8 


154 


8 


154 


10 


15% 


10 


21 


T 


6 


10 


6 


is 1 .; 


6 


154 


7 


15% 


8 


21 


U 


8 


10 


8 


154 


9 


154 


10 


15% 


10 


21 


V 


7 


10 


7 


154 




154 


9 


15% 


9 


21 


W 


12 


12% 


12 


' 15i:; 


13 


194 


15 


19% 


15 


25 


X 


8 


10 


8 


154 


9 


154 


9 


15% 


9 


21 


Y 


6 


10 


6 


154 


6 


154 


7 


154 


8 


21 


Z 


8 


10 


8 


154 


8 


1514 


9 


15% 


11 


21 


& 


8 


10 


8 


154 


9 


154 


9 


154 


10 


21 


1 


4 


10 


4 


is 1 ; 


4 


3514 






5 


21 


2 


9 


10 


8 


154 


8 


15*4 






11 


21 


3 


9 


10 


7 


154 


7 


154 






9 


21 


4 


7 


10 


7 


154 


7 


15% 






11 


21 


5 


10 


10 


10 


154 


10 


15% 






12 


21 


6 


9 


10 


8 


154 


9 


154 






11 


21 


7 


6 


10 


6 


154 


G 


15% 






8 


21 


8 


11 


10 


11 


154 


8 


154 






10 


21 


9 


9 


10 


8 


154 


9 


154 






11 


21 


$ 


8 


10 


8 


154 

154 


8 


15% 

154 






8 


21 



The supporting cable is usually attached to the 
electric sign somewhat back of its outer end, and it 
may be assumed that the cable carries about 60 per 
cent of the wezght of sign. Y7 ith this assumption and 



208 ELECTRICAL TABLES AND DATA 

using a safety factor of 5, the strength of the cables 
necessary to support it can be found by the formula : 



S - 5 x .60 x W- 



II 

where W = weight of sign; II = height of attachment 
to wall above sign, and D = the distance from attach- 
ment on sign to a point vertically under sign support. 
Table LXVIII is calculated according to this for- 
mula (omitting W), and to find the proper cable to 
support a given sign it is but necessary to multiply 
number found at intersection of line pertaining to 
height of support and that pertaining to distance of 
sign attachment from wall, by the weight of sign. 
The result will give the breaking strain of the neces- 
sary cable. 

TABLE LXVIII 

Supports for Weight of Sign. 
Distance 
from Wall to 

Attachment on Height of Cable Fastening Above Sign in Feet 
Sign in Feet 

3 4 5 6 8 10 12 14 16 IS 20 

4 5 4 4 3.6 3.4 3.2 3.0 3 3 3 3 

5 6 5 4.2 3.7 3.5 3.3 . 3.2 3 3 3 3 

6 7 5.4 5.0 4.2 .3.8 3.5 3.4 3.2 3 3 3 

7 8' 6.0 5.1 4.7 4.0 3.7 3.5 3.4 3.3 3 3 

8 8.6 6.8 o.7 5.0 4.2 4.0 3.6 3,5 3.4 3.3 3 
10 10.5 8.1 6.9 6.0 5.0 4.4 3.9 3.8 3.6 3.4 3.3 
12 12.4 9.4 7.8 6.7 5.4 4.6 4.3 4.0 3.7 3.5 3.4 
14 14.6 11.1 9.0 7.8 6.0 5.2 4.8 4.1 4.0 3.9 3.7 

SIDE GUYS FOR SIGNS 

The wind pressure on the ordinary sign must be 
calculated on the basis of 20 lbs. per square foot and 
requires much better supports to withstand it than 
are necessary to support the weight of sign, although 
they are never so provided. 



ELECTRICAL TABLES AND DATA 209' 

The table below has been calculated according to the 
same general formula as the one above. To find the 
proper size of cable for side guys, multiply the num- 
ber of square feet in sign by number found where 
lines pertaining to the two fastenings of side guys* 
cross. 







TABLE LXIX 












Distance of 




















Attachment on 


Distance c 


f Guy Attachment on Wall from> 


Sign from Wall 






Sigr 


l in 


Feet 












3 


4 


5 6 


7 


8 


10 


12 


14 


16 


2 


17 


17 


16 15 


15 


14 


14 


14 


14 


14 


3 


21 


18 


18 17 


16 


15 


14 


14 


14 


14 


4 


24 


20 


18 17 


16 


16 


15 


15 


14 


14 


5 


27 


22 


20 19 


18 


17 


16 


16 


15 


14 


6 


31 


25 


22 20 


19 


18 


17 


16 


15 


15 


7 


34 


28 


24 22 


20 


19 


18 


17 


16 


15 


8 


38 


32 


27 24 


21 


19 


18 


17 


17 


16 


9 


44 


35 


29 26 


22 


21 


19 


18 


18 


17 


10 


48 


3S 


32 28 


24 


23 


20 


19 


18 


17 


12 


57 


45 


37 33 


27 


25 


22 


21 


19 


18 



For signs hung at corners the distance of guy 
attachment on wall must be taken as the point at 
right angles to sign where the guy would strike wall 
if it were at right angles to sign. 



TABLE LXX 

Table showing approximate strength in pounds of 
Standard Steel Strand — American Steel & Wire Co. 



Diameter 


Approximate 


D^ 


ameter 


Approximate 


in Inches 


Strength 


in 


Inches 


Strength 


§ 


8,500 lbs. 




3 7 2 


1,800 lbs. 


ts 


6,500 lbs. 




ft 


1,400 lbs. 


§ 


5,000 lbs. 




3 5 2 


900 lbs. 


- 5 -v 

i 


3,S00 lbs. 
2,300 lbs. 




1 
8 


500 lbs. 
400 lbs. 



210 ELECTRICAL TABLES AND DATA 

Cable Supports for Signs Over Streets. — Signs of 
this kind are usually supported from steel cables swung 
across street, or other open place, from the tops of 
buildings or suitable poles. The table below gives the 
stresses caused by various loads per foot evenly dis- 
tributed, and also for loads suspended from center. 
The arrangement of sign is usually such that neither 
case exactly applies, so that an approximate mean of 
the two must be taken. The calculations are for a 
100-foot span and a sag of 4 feet. 









TABLE LXXI 






Diam- 






Stress 








eter 


Wt. 


Approxi- 


Caused by 








of 


per 


imate 


Cable Distributed Load 


Load ir 


Center 


Cable 


Foot 


Strength 


Alone Poun 


ds Stress 


Pounds 


Stress 


If 


4.85 


84,000 


1,500 50 


17,140 


2,500 


15,625 


1+ 


3.55 


60,000 


1,109 30 


10,484 


1,500 


9,375 


U 


2.45 


46,000 


766 20 


7,015 


1,000 


6,250 


1 


1.58 


28,000 


493 15 


5,181 


750 


4,687 


1 


1.20 


22,200 


375 12 


4,125 


600 


3,750 


t 


0.89 


15,600 


278 9 


3,090 


500 


3,125 



The above figures represent the maximum loads 
which should be suspended by such cables unless a 
greater sag is allowed, and do not take wind pressure 
into consideration. See "Side Guys." 

The above figures are based on the following for- 
mulae used by American Steel and Wire Co. : 

S x = -Q-j- giving stress for evenly distributed load, and 

oCl 

Wl 

S 9 = -rr- for stress due to load in center. 
2 4d 

S = stress on cable 

W = weight per foot of cable and load if evenly dis- 
tributed, or load in center 
I- length of span 
<2= sag in feet. 



ELECTRICAL TABLES AND DATA 211' 

To find total stress those due to cable and load must 
be added. 

Slide Rule. — Figure 22 is an illustration of the 
ordinary slide rule. The numbers on the top, or A, 
scale, may be read naturally as 1, 2, 3, 4, etc., ending 
with the last figure 1 at the right, which would then be 
called 100, or these values may be considered in- 
creased or decreased to any extent by adding or 
prefixing the necessary number of ciphers. Thus if 
the 2 is called 20 or 200 the 3 would be called 30 or 
300, etc. The same also hclds true of the upper half 
of the slide, or B scale. The divisions between the 
main figures are of various dimensions, but serve only 




Figure 22. — The Slide Rule. 



to designate fractional values of the figures. The- 
principle of operation can easiest be made clear by 
examples. 

Multiplication. — Set the 1 on upper half of slide 
under one of the factors on scale A. Find the other 
factor on the slide and directly above it you have the 
product. Multiply 4 by 2. Setting the slide as 
directed we find 8. This same setting might be used 
to multiply 40 by 20, or 4000 by 2 or 200. "We have 
but to note as we go along by how much we increased 
the value of either of the factors, and add the cor- 
responding number of ciphers. Different settings 
could also be used for the same problem. Consid- 
erable practice is necessary before one can become; 
really proficient in these calculations. 

Division. — In division the above process is reversed. 
Place the divisor on the slide under the dividend on 



212 ELECTRICAL TABLES AND DATA 

scale A and the 1 on slide will be directly below the 
quotient. 

Multiplication and Division Combined. — 

^ , 7x3x4 
Sample: — ^ 

Set 1 on slide under 7, note product above 3 ; next 
<set 1 on slide under this product and note product 
above 4. Now move slide back until 6 is under last 
product and find answer above 1. 

Proportion. — By setting any number on B against 
any convenient number on A it can be seen that all 
other coinciding numbers are in the same proportion 
to each other. Hence any problem in direct propor- 
tion can be solved by simply setting the first term on 
B against the second on A; this being done, we shall 
find the last term directly above the third on B. 
Example : If 7 bushels of wheat cost $13.00, how 
much will 23 bushels cost? Answer, $42.71. In 
direct proportion all factors are either increasing or 
decreasing. If they are mixed it is termed Inverse 
Proportion. In order to solve a problem in inverse 
proportion we invert the slide, but continue to read 
A and B together. Example: If 9 men can do a 
piece of Work in 17 days, how many days will 13 
men require? Inverting the slide and setting the 9 
on the left under 17 and bringing the runner over the 
13 at the right at about the center of the scale, we find 
11.8 as the answer. 

Squaring Numbers and Extracting Square Boots. — 
When the slide is set even on all sides, the numbers 
in the scales A and B are the squares of those in 
C and D» Hence also those in the last named scales 
are the square roots of the upper. They must, how- 
ever, be taken with the proper number of ciphers. 
The square of 2, for instance, is 4, that of 20 is 400 



ELECTRICAL TABLES AND DATA 213 

and that of 200 equals 40,000. In extracting square 
roots, if the number of digits is odd, 4, 400, etc., the 
root will be found directly under the number on left 
hand side of scale. If the number of digits is even, 
it will be found on right hand side, viz., square root 
of 40 equals 6.41. 

Extracting Cube ^Root. — Set the runner on the 
number, the root of which is to be found, and shift the 
slide until the same number found under this num- 
ber is also found under the index of the slide on the • 
lower part D. According to location of runner either 
the right or left hand index must be used. Practice 
raising number to the third power; reversing this 
process will show method of extracting roots. 

Sockets. — Nearly all lamps used in this country 
are fitted with the well-known Edison base. A few 
old installations equipped with the T.H. base still 
remain, but are usually equipped with adjusters to 
permit the use of Edison base lamps. 

The standard sockets as recognized by the N. E. C. 
are given below: 

Classification. — Sockets to be classed according to 
diameters of lamp bases, as Candelabra, Medium and 
Mogul. Base to be known respectively as -J- inch, 
1 inch and 1J inch nominal sizes, with ratings as 
specified in the following table: 



, Eatings ■> 

Key Keyless 

Max. Max. 
Amp. Amp. 
at any at any 
Nominal Volt- Volt- 
Class Diam. Watts Volts age Watts Volts age 



Candelabra i in. 75 


125 


f 


75 


125 


1 


Medium 1 " 250 


250 


2* 


660 


250 


6 


(a)660 


250 


6 


660 


600 




Mogul 1^ in. 






1,500 


250 




(b) 






1,500 


600 





214 ELECTRICAL TABLES AND DATA 

(a) This rating may be given only to sockets having a 
switch mechanism which produces both a quick "make" and 
a quick "break" action. 

(b) Eatings to be assigned later, pending further discus- 
sion with manufacturers. 



Miniature sockets and receptacles having screw 
shells smaller than the candelabra size may be used 
for decorative lighting systems, Christmas tree light- 
ing outfits, and similar purposes. 

Double-ended Sockets. — Each lamp holder to be 
rated as specified above, the device being marked with 
a single marking applying to each end. 

In addition to these there is the Edi-Swan base, 
which is f inch diameter, and has bayonet-type con- 
nections and is sometimes used on automobiles and 
other places where there is much jarring. The Edison 
miniature base is f inch in diameter and is used only 
for low voltages. Some very small lamps are made 
without bases, the wires connecting direct to lamp 
terminals. The mogul socket is used for series in- 
candescent lighting and often fitted with automatic 
cut-out. It is also used for gas-filled lamps of 300 
watts or over. Fiber lined or brass shell sockets 
should not be used in damp places, or where corrosive 
vapors exist. Key sockets should also be avoided in 
damp places, or where inflammable gases may exist. 

Sparking Distances. — Very high-test voltages are 
often measured by their sparking distance. The fol- 
lowing table gives the sparking distances between 
sharp points corresponding to different alternating 
current voltages, when the ratio between maximum 
and mean effective voltages is equal to 1.41, or the 
square root of two. The values given were derived 
from a long series of careful and accurate tests. 



ELECTRICAL TABLES AND DATA 







TABLE LXXII 








(Copyright, 1906, by Standard 


Underground Cable Co.) 




Spark 




Spark 




Spark 


Volts 


Distance 


Volts 


— Dist 


ance — 


Volts 


— Distance — 




A. or B. 




A. 


B. 




A. 


B. 


1,000 


0.028 


18,000 


0.945 


0.945 


35,000 


1.840 


1.895 


2,000 


0.098 


19,000 


0.995 


0.995 


36,000 


1.900 


1.958 


3,000 


0.159 


20,000 


1.042 


1.042 


37,000 


1.945 


2.020 


4,000 


0.216 


21,000 


1.092 


1.097 


38,000 


2.012 


2.085 


5,000 


0.270 


22,000 


1.143 


1.150 


39,000 


2.062 


2.153 


6,000 


0.324 


23,000 


1.195 


1.206 


40,000 


2.127 


2.220 


7,000 


0.378 


24,000 


1.247 


1.260 


41,000 


2.190 


2.290 


8,000 


0.432 


25,000 


1.300 


1.314 


42,000 


2.247 


2.360 


9,000 


0.487 


26,000 


1.353 


1.373 


43,000 


2.308 


2.434 


10,000 


0.540 


27,000 


1.405 


1.427 


44,000 


2.370 


2.506 


11,000 


0.595 


28,000 


1.460 


1.485 


45,000 


2.432 


2.580 


12,000 


0.644 


29,000 


1.512 


1.540 


46,000 


2.495 


2.660 


13,000 


0.695 


30,000 


1.566 


1.600 


47,000 


2.560 




14,000 


0,746 


31,000 


1.620 


1.655 


48,000 


2.625 




15,000 


0.797 


32,000 


1.675 


1.712 


49,000 


2.692 




16,000 


0.845 


33,000 


1.728 


1.772 


50,000 


2.760 




17,000 


0.897 


34,000 


1.785 


1.833 









SPARKING DISTANCES IN INCHES. 

Column A gives spark distances with 10 inch con- 
cave metal shields, the plane of whose edges was 1 inch 
"back of the needle points. Column B gives the spark 
distances without shields. 

Sharp needles are essential for uniform spark dis- 
tances, as points measuring from 0.001 inch to 0.002 
inch gave in many instances spark distances that 
were from 20 to 45 per cent greater than those ob- 
tained with sharp points. See also table of A. I. E. E. 
in Standardization Recommendations. 

Specific Gravity (Solids). — The specific gravity of 
a substance is defined as the ratio of the weight of that 
substance to the weight of an equal volume of water 
or air. Water is used as the standard of liquids and 
solids. Air at the temperature 0°, C. (32° F.) and 
766 mm. mercury pressure for gases. By multiplying 
the specific gravity of any substance by the weight 



216 ELECTRICAL TABLES AND DATA 

of an equal volume of water we find the weight of 
that volume of the material. The weight of a cubic 
foot of water is approximately 62.5 lbs. The weight 
of a gallon is approximately 8.33 lbs. To find the 
specific gravity of a body heavier than water approx- 
imately by experiment, weigh it in air and then weigh 
it in pure water. Divide the weight in air by the 
loss of weight (buoyancy) in water and the quotient 
will give the specific gravity. If the body is lighter 
than water load it down with a substance heavy 
enough to sink it. Then weigh the two submerged 
together. Also weigh both separately in air and the 
heavy body in water. Subtract the buoyancy of the 
heavy body from the buoyancy of the two bodies to- 
gether. The remainder will be the buoyancy of the 
lighter body by which its weight in air is to be divided 
as before. 

Specifications. — In many cases preliminary specifi- 
cations, setting forth what the purchaser desires, are 
made out. Unless these are quite broad many dealers 
or manufacturers may not be able to comply with 
them and for this reason often submit specifications 
of their own, and thus the final specifications which 
form the basis of contracts must be somewhat modi- 
fied. 

In general, specifications may be divided into two 
parts: one part which deals with machinery and 
materials, and another which deals with the installa- 
tion work and results to be obtained. If certain 
materials are specified, and at the same time require- 
ments as to certain results are made, there is always 
a chance for disputes as to who is responsible in case 
the installation does not fulfill requirements. Unless 
the work is to be carried on under the supervision of 
a consulting engineer, it is best to give the contractor 
free choice of materials and hold him entirely re- 
sponsible for the final result. 



ELECTRICAL TABLES AND DATA 21? 

All specifications should be based upon the stand- 
ards of the engineering societies governing the par- 
ticular kind of work. The A. I. E. E. have standard- 
ization rules which govern everything electrical, but 
these do not largely concern themselves with safety 
rules. In this regard the National Electrical Code 
should be adopted as the standard and all material 
and workmanship should be specified to conform with 
its requirements. This is a reliable guide in every 
respect except that of economy and efficiency and 
suitability of systems, etc. It deals only with safety 
and reliability. 

It is best always to have some sort of a plan show- 
ing location of cut-out centers, switches, lights and 
motors, or any other parts about which there may 
afterwards be disputes. If there are no plans the 
location of cut-outs and other conspicuous elements 
should be mentioned in the specifications. They 
should also mention how much conduit, open or mold- 
ing work is to be used. Every item mentioned should 
form a clause and these should be numbered for 
reference. 

Where accurate calculations are to be made, all 
circuits and runs of wire should be measured and the 
specifications thoroughly read and considered. The 
estimator should take plenty of time to understand 
every phase of his job. As a reminder of the many 
items so easily overlooked, he should have prepared 
an estimate sheet on the order of that following which 
is furnished by courtesy of the National Electrical 
Contractors ' Association. Large apartments, hotels, 
etc., usually have many floors and rooms which are 
exact duplicates, and very careful measurements of 
one floor or room will answer for the whole building 
or that part of it which is typical. 

Table LXXIII shows approximate quantities of" 
material used for rough wiring in average flats. 



ELECTRICAL TABLES AND DATA 



P?3 








»>a 3 


XS™, 




n K " 


?BB 




B 8.-« 


cog 


ssrs 






I °EL 






1 s-l 






fen 


g.g-s 


^jf 3 * 


&^ 






i-sg- 


as& 


l»s. 




° 3 








S" 65 






B-g* 



££££ ££ 


rfc£ >££ 


^ 




1 


KWWW £?£?£?£? c?c?c?<? 












.. 


PT PT t»7* pt* £§ 2J sf Q £§ £5 §" £5 


H 
SO 


1 » 


m&Zfr KKKK ££££ 


o 


1 B 


Z!zJS5^ jTfTpS- I'i-i'S" 


tr 1 


* n 


. - »S- s.3.2.^ o o o o 


H 

5 


o 2 

* 3 


- - -ff S-g-g-.w 




w 2 


ches, Condi 
les, K and 
hes, K and 
hes, Mould 

les, Condu 
Kand 
Kand 
Mould 


i. 


$ 


a 







w 2 

s8 


£c 


ndui 
and 
and 
ould 

it 

Tube 
Tub 
ng 

t.. 
Tub 








it*' : •- 


3 V; \ 


5 2g 

erg" 




P 








•go 








s?s 


>*>•; ts3N 


»»: 8 


g^s 




Ft. Single Wire. 




• to " ■ 


: *" : 


: : s 


Ft. Twin Wiee. 


• N 


00- • Is 


&■■ ! 


isooo 




Ft. Loom. 


~i 


'• • U>; 


; • 00; ; 




Ft. Moulding. 


5C 


t-i' 'a 


-^: 


-<I00 




No. Insulators. 


a 


$j tot: 


£: t- 


3h^O 




No. Tubes. 




s 


: £ : 




In 


Ft. Conduit. 




: - : ! 


: - : 




H* 


No. Elbows. 












No. Outlet 




: *" : : 


: ^ : 




1-1 


Boxes. 














No. Lock Nuts 




: ** : : 


. ^ . 




*" 


and Bushings. 












No. Couplings, 




: *i : : 


: *■* : 




M 


Extra 








*\ **+ 




Lb. Nails. 


*■: 


': : ■*: 










Oz. Brads. 














Rolls Tape, 














Each Kind. 



ELECTRICAL TABLES AND DATA 



National Electrical Contractors' Association Universal 
Estimate Sheet. 



Bid Goes to 

Address 

No. Lights Architect or Engineer . 



No! Base Plugs'.'.'.'. Name of Job Or Building Estimate No.. 

No. Telephones... .L 0cat i 0n f Job of Building.. Sheet No 

No. Motors _. T, r mil -NT- 
Mr Telephone No.... Date 19. 



Switchboard 



'Salesman 1 j b No. 



Material Estimated by Labor Estimated by Priced by Approved by- 



Conduit, Rigid 
Conduit Elbows 
Conduit Bushings 
Conduit Straps 
Conduit Hangers 
Lock Nuts 
Conduit Flexible 
Conduit Fittings 
Conduit, Non-Metallic 
Ceiling Boxes 
Bracket Boxes 
Switch Boxes 
Floor Boxes 
Box Covers 
Fixture Hangers 
Cutout Cabinets 
Panelboards 
Metering Panels 
Meter Loops 
Cutout Boxes 
Asbestos 
Cut Out Blocks 
Fuse Plugs 
Enclosed Fuses 
Flush Switches 
D. P. Flush Switches 

3 Way Flush Switch 

4 Way Flush Switch 
Snap Switches 

D. P. Snap Switches 

3 Way Snap Switch 

4 Way Snap Switch 



Knife Switches 
Door Switches 
Pendant Switches 
Rubber Covered Wire 
Lead Covered Wire 
Fixture Wire 
Special Wire 
Lamp Cord 
Reinforced Cord 
Packing House Cord 
Show Window Cord 
Molding Wood 
Molding Metal 
Molding Fitting 
Fixtures 
Clusters 
Key Sockets 
Keyless Sockets 
Wall Sockets 
Rosettes 
Socket Bushings 
Cord Adjusters 
Shades 
Shadeholders 
Adapters 

Attachment Plugs 
Lamps, Incandescent 
Lamp Guards 
Arc Lamp 
Cleats 
Knobs 
Tubes 



Screws 

Nails 

Toggle Bolts 

Annunciators 

Annunciator Wire 

Annunciator Cable 

Elevator Cable 

Bells 

Buzzers 

Push Buttons 

Silk Cord 

Door Openers 

Burglar Alarm 

Batteries 

Bell Ringers 

Telephones 

Telephone Cable 

Speaking Tube 

Whistles 

Letter Boxes 

Tape 

Solder 

Compound 

Acid 

Oil 

Car Fare 

Cartage 

Bond 

Drafting 

Inspection 

Incidentals 



Bid Sent to Following: 



Total 

Material 

Labor 

Overhead Expenses 

Profit 

Bid 



220 ELECTRICAL TABLES AND DATA 

Figures 23, 24 and 25 will assist in illustrating the 
most economical manner of running wires for branch 
circuits. In Figure 23 the heavy black lines denote 
the mains, and at their terminals the cut-outs are 
located. It is never economical to push mains any 
farther than is necessary to enable one branch circuit 
to reach the far end of the space to be covered. In 
the arrangement shown in Figure 23 the greatest 
possible economy would be effected if a cut-out were 




Figure 23. — Comparison of Materials. 

provided for each circuit, but for various reasons 
this is not advisable. The next best arrangement is 
to provide a number of cut-out centers as shown in 
the figure, locating each cut-out in the center of the 
group it is to supply. 

" In case a given number of lights are to be fed with 
wires running at right angles, the most economical 
arrangement can be found by running a straight line 
through the space covered at such point as to leave 
an equal number of lights on each side of it, as in 
Figure 24. 

If the lights are to be fed by diagonal runs, the 
shortest runs can be quickly found by bearing in 



ELECTRICAL TABLES AND DATA 



mind that from the cut-out center, or from any outlet, 
this point in connection with any two other outlets 
forms a triangle and it is merely necessary to avoid 
using the longest side of this triangle. The position 



X3— 



r-0 

a 



s-. 

G — 



fr- 



76 ft 



— a 



-s 



Figure 24. 




Figure 25. 

of lamps shown in Figures 24 and 25 is identical, but 
Figure 25 requires about 10 per cent less material 
than Figure 24. The relative economy of running 
mains or branch circuits can be determined by Table 
LXXIV, which gives the equivalent in mains of vari- 
ous sizes and branch circuits of 660 watt capacity. 



ELECTRICAL TABLES AND DATA 



TABLE LXXIV 



Showing Mains and Their Equivalent in No. 14 Branch 
Circuits. 



2 Wire 
Mains Branches 



2 ft. No. 
2 ft. No. 
2 ft. No. 
2 ft. No. 
2 ft. No. 
2 ft. No. 
2 ft. No. 
2 ft. No. 
2 ft. No. 
2 ft. No. 
2 ft. No. 
2 ft. No. 
2 ft. No. 



14= 4 ft. No. 14 

12= 6 ft. No. 14 

10= 8 ft. No. 14 

8=10 ft. No. 14 

6=16 ft. No. 14 

5=18 ft. No. 14 

4=22 ft. No. 14 

3=26 ft. No. 14 

2=30 ft. No. 14 

1=32 ft. No. 14 

0=40 ft. No. 14 

00=50 ft. No. 14 

000=58 ft. No. 14 



3 Wire 
Mains Branches 



3 ft. No. 
3 ft. No. 
3 ft. No. 
3 ft. No. 
3 ft. No. 
3 ft. No. 
3 ft. No. 
3 ft. No. 
3 ft. No. 
3 ft. No. 
3 ft. No. 
3 ft. No. 
3 ft. No. 



14= 10 ft. No. 14 

12= 12 ft. No. 14 

10= 16 ft. No. 14 

8= 22 ft. No. 14 

6= 32 ft. No. 14 

5= 36 ft. No. 14 

4= 44 ft. No. 14 

3= 52 ft. No. 14 

2= 60 ft. No. 14 

1= 64 ft. No. 14 

0= 80 ft. No. 14 

00=100 ft. No. 14 

000=116 ft. No. 14 



2 ft. No. 0000=74 ft. No. 14 



3 ft. No. 0000=148 ft. No. 14 



Street Lighting. — In villages and suburbs, the 
street lighting is often of a perfunctory nature. It 
consists often merely of an incandescent or arc lamp 
placed at each street intersection. Such lights should 
be over center of streets. In parks, the object of the 
illumination must be not merely the road or path, but 
fields and lagoons as well. At band-stands and sim- 
ilar places, arc lamps are preferable, but where the 
lights must be brought down under trees they are not 
very serviceable. Along curved driveways place 
lights on the outer curve; this will enable drivers to 
see farther, but will require more material. 

In business streets a very brilliant illumination is 
often desired. Tungsten lamps, installed on posts, 



ELECTRICAL TABLES AND DATA 223 

are the most common illuminants at present where 
a permanent installation is contemplated. For tem- 
porary effects festoons are much used. The systems 
upon which such lights are operated will usually be 
governed by that which is already in use. The fol- 
lowing points should be noted in connection with 
street lighting: Large units are most economical in 
first cost, but waste much of their light outside of "the 
street. At street intersections this waste is not so 
great. Large units should always be hung high. A 
bright illumination, except on business streets, is not 
necessary, but the light should be white. For series 
incandescent lighting special lamps are always used. 
The thicker the filament the less will the flickering 
effect of low frequencies affect them. For overhead 
work wires smaller than No. 6 are seldom used. No 
incandescent lamp should ever be used outside without 
a reflector to prevent light being wasted on the upper 
air. Time switches are often serviceable on street 
lighting. Those who undertake to install a system 
of street lighting should prepare themselves for an 
unlimited amount of annoyance from residents who 
imagine their trees will be ruined or who quarrel 
about the location of poles and lamps. 

Switches. — The standard height of switches in 
offices and residences is 4 ft. 6 in. above finished floor. 
If switches of the push button type are used the white 
button should be uppermost. Switches should con- 
tain sufficient metal to prevent a temperature rise 
of over 28° C. (50° F.). There should be a contact 
surface of about 1 sq. in. for every 75 amperes. To 
obtain this contact surface large capacity switches 
are made up of a number of blades in parallel. This 
arrangement also allows better radiation. The fol- 
lowing table shows the capacity of single blades of 
dimensions given, the clip being assumed as of some 
width. 



ELECTRICAL TABLES AND DATA 



TABLE LXXV 



Width, in...i § 
Ampere^ 8 15 



i f 

30 58 



11 1 U 11 If li If 
85 115 150 180 215 280 330 395 



These widths will not determine capacity of switch 
unless the temperature rise is within the limits. 
Below are given the dimensions and spacings of knife 
switches as required by the N. E. C. Over all dimen- 
sions of standard knife switches as made by the George 
Cutter Company are given on pages 226 and 230. 

Spacings and Dimensions. — Spacings and dimen- 
sions must be at least as great as those given in the 
following tables: 



TABLE LXXVI 

Not over 125 volts d. c. and a. c. 
For switchboards and panel boards: 





Minimum 
separation of 
nearest metal 
Width and Thickness parts of 
Clips opposite 
Blades and Hinges polarity 


Minimum 

break 
distance 


30 amp 

60 amp.. . . 


. . . ^x s 5 i in. *x B 3 5 in. 

TABLE LXXVII 


1 in. 
Uin. 


fin. 
1 in. 



Not over 125 volts d. c. and a. c. 
For individual switches: 

Inch Inch Inch Inch 

30 amp $x& ix B 3 5 1£ 1 

60 & 100 amp li li 

200. amp U 2 

400 & 600 amp. 2| 2£ 

800 & 1000 amp 3 2| 

A 300-ampere switch with the spacings of the 
200-ampere switch above may be used on switchboards. 



ELECTRICAL TABLES AND DATA „£, 

TABLE LXXVIII 

250 volts only d. c. and a. c. 
For all switches: 

Inch Inch Inch Inch 

30 amp Jx G 5 5 Jx^ If 1J 

TABLE LXXIX 

Not over 250 volts d. c. nor over 500 volts a. c. 
For all switches : 

Inch Inch Inch Inch 

30 amp fx| fx T V 2i 2 

60 & 100 amp 2£ 2 

200 amp 2* 2\ 

400 & 600 amp 2f 2* 

800 & 1000 amp 3 2| 

A 300-ampere switch with the spacings of the 200- 
ampere switch above may be used on switchboards. 

Cut-out terminals on switches for over 250 volts 
must be designed and spaced for 600-volt fuses. 

TABLE LXXX 

Not over 600 volts d. c. and a. c. 
For all switches: 

Inch Inch Inch Inch 

30 amp fx* fx^ 4 3£ 

60 amp * 4 3 \ 

100 amp 4£ 4 

Auxiliary contacts of either a readily renewable 
or a quick-break type or the equivalent are recom- 
mended for d. c. switches, designed for over 250 volts, 
and must be provided on d. c. switches designed for 
use in breaking currents greater than 100 amperes 
at a voltage of over 250. 

For 3-wire direct current and 3-wire single phase 
systems the separation and break distances for plain 
3-pole knife switches must not be less than those 
required in the above table for switches designed for 
the voltage between neutral and outside wires. 



ELECTRICAL TABLES AND DATA 

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ELECTRICAL TABLES AND DATA 



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232 ELECTRICAL TABLES AND DATA 

Switchboards. — The best material for mounting 
switches and bus-bars is marble. Slate may be used, 
but metal veins may cause trouble. A liberal allow- 
ance of space should be allowed back of board, and 
its panels should be kept well above the floor. Where 
more than one machine is connected it is customary 
to operate them in parallel on d. c. For dimensions 
of bus-bars, switches and fuses, see those headings. 
It is customary to provide the following instruments, 
etc., for good switchboards : One main three pole 
switch for each generator, where there are several 
operated in parallel. One ammeter for each gen- 
erator, or an ammeter arranged for connection to 
each machine. A voltmeter which may be connected 
to any machine, and also be used as a ground detector. 
One field rheostat for each machine. Sufficient pilot 
lights to illuminate board properly. In some cases 
also a wattmeter measuring the total current. 

Alternating current boards are also often equipped 
for parallel running, but not always. In some cases 
the board is divided and fitted with throw over 
switches so that either generator may supply every- 
thing connected, or only a part of it, as desired. 

The following equipment is commonly used : Main 
switch for each generator. Synchronizing lamps, or 
synchroscope. Frequency indicator. Power factor 
indicator. Voltmeter to be used as with d. c. machines. 
An ammeter for each phase, and also for each gen- 
erator. Exciter equipment. Wattmeters. To these 
must of course be added the necessary fuses and 
switches. The N. E. C, however, does not require 
fuses on a. c. generator or their exciters. If prac- 
ticable, light and power circuits should be kept 
separate. 

Symbols. — The following are the symbols recom- 
mended by the American Institute of Electrical 
Engineers. 



ELECTRICAL TABLES AND DATA 233 

The following notation is recommended : 

Name of quantity Symbol Unit 

Voltage, e.m.f., potential cliff erence .... E, e, volt 

Current I, i, ampere 

Eesistance R, r, ohm" 

Reactance X, x, ohm 

Impedance Z, z, ohm 

Admittance . Y, y, mho 

Conductance G, g, mho 

Susceptance B, b, mho 

Power P, p, watt 

Capacity C, c, farad 

Inductance L-, henry 

Magnetic flux <j> maxwell 

Magnetic density B gauss 

Magnetic force II gilbert per cm. 

Length L, 1, cm. or inch 

Mass M, m, gm. or lb. 

Time . . . T, t, second or hour 

Em, Im and Bm should be used for maximum cyclic 
values, e, i and p for instantaneous values, E and I 
for r. m. s. values, and P for the average value or 
effective power. These distinctions are not necessary 
in dealing with continuous current circuits. Vector 
quantities are preferably represented by bold face 
capitals. 

Testing. — It is assumed that the reader of this 
work is familiar with the general principles employed 
in testing, and therefore no attempt will be made to 
explain methods of using the various instruments. 
The list given in the following pages is intended as a 
reminder of the various instruments available for 
different purposes. Those about to undertake testing 
work with which they are not entirely familiar are 
advised to consult this list, and select those instm^ 
ments needed. Consult Standardization Rules of 
A. I. E. E. and N. E. C. and make tests in conformity 
with their standards. 



234 ELECTRICAL TABLES AND DATA 

STANDARD SYMBOLS FOR WIRING PLANS 

AB adopted and recommended by the National Electrical Contractohs 

Association of the United States. 

y^K Ceiling Outlet; electric only. Numeral in center indicates 
x£/ number of standard 16 c. p. incandescent lamps. 

4 Ceiling Outlet; combination. 4-2 indicates 4-16 c. p. stand- 



HU 



IT 



ard incandescent lamps and 2 gas burners, 

Bracket Outlet; electric only. Numeral in center indicates 
number of standard 16 c. p. incandescent lamps. 

4 Bracket Outlet; combination. 4-2 indicates 4-16 c. p. stand* 
7T ard incandescent lamps and 2 gas burners. 

Wall or Baseboard Receptacle Outlet. Numeral in center 
indicates number of standard 16 c. p. incandescent lamps. 

Floor Outlet. _ Numeral in center indicates number of stand- 
ard 16 c. p. incandescent lamps. 

6 Outlet for Outdoor Standard or Pedestal; electric only. 
Numeral indicates number of stand. 16 c. p. incan. lamps. 

B Outlet for Outdoor Standard or Pedestal; combination. 
yQff "#• 6-6 indicates 6-16 c. p. stand, incan. lamps; 6 gas burners. 

)J3f Drop Cord Outlet. 



m 



3 



One Light Outlet, for lamp receptacle. 
Arc Lamp Outlet, 

Special Outlet, for lighting heating and power current, as 
described in specifications. 



^^^"^^QCeiling Fan Outlet. 
2 ' S. P. Switch Outlet. 
Q2 D. P. Switch Outlet. 
Q 3 3-Way Switch Outlet. 
O 4 4-Way Switch Outlet. 



Show as many symbols as there are 
switches. Or in case of a very 
large group of switches, indicate 
number of switches by a Roman 
numeral, thus: SI XII; meaning 
12 single pole switches. 

Describe type of switch in specifi- 
cations, that is, 

Flush or surface push button or 
snap. 



Copyright 1906 by the National Electrical Contractors' Association of to© 
United States, Published by permission. 



ELECTRICAL TABLES AND DATA 235 

STANDARD SYMBOLS FOR WIRING PLANS 

As adopted and recommended by the National Electrical Contractors 

Association of the United States. 



S 



Automatic Door Switch Outlet. 



2 Electrolier Switch Outlet. 

^m Meter Outlet. 

; H| Distribution Panel. 

J Junction or Pull Box. 
\j5jf Motor Outlet; numeral in center indicates horsepower 
] Motor Control Outlet. 
^T"|^ Transformer. 
■«^— ^ «^B™^™»Main or feeder run concealed under floor. 
•■^■■■■■■■■■■■■m Main or feeder run concealed under floor above* 
■» ■» ■■» ■» ■»••■• Main or feeder run exposed. 
Ife ■ Branch circuit run concealed under floor. 

"- ' ■ Branch circuit run concealed under floor above. 

«■■" — "■ — — — — "■"• Branch circuit run exposed. 
b* -•• — — — — ♦ — — Pole line. 

• Riser. 
Suggestions in Connection with Standard Symbols for Wiring Plans. 

Indicate on plan, or describe in specifications, the height of all outlets 
located on side walls. 

It is important that ample space be allowed for the installation of mains. 
feeders, branches and distribution panels. 

It i3 desirable that a key to the symbols used accompany all plans. 

If mains, feeders, branches and distribution panels are shown on thia 
plans, it is desirable that they be designated by letters or numbers. 



236 ELECTRICAL TABLES AND DATA 

STANDARD SYMBOLS FOR WIRING PLANS 

As adopted and recommended by the National Electrical Contbactojw 

Association of the United States. 

Kj Telephone Outlet; private service. 



8 



Telephone Outlet; public service. 
BeU Outlet 



f~V Buzzer Outlet. 

I ©1,2' Push Button Outlet; numeral indicates number of pushes* 
m- i^qS Annunciator; numeral indicates number of points, 
i — M Speaking Tube. 
*&~/q\ Watchman Clock Outlet. 
— i T Watchman Station Outlet. 
*— (fc) Master Time Clock Outlet. 
—In Secondary Time Clock Outlet 

I f I Door Opener. 

RFj Special Outlet; for signal systems, as described in specifications 
J | I | I |Battery Outlet. 

( Circuit for clock, telephone, bell or other service, 
1 run unde- floor, concealed. 
I Kind of service wanted ascertained by symbol to 
which line connects. 

Circuit for clock, telephone, bell or other service, 
run under floor above concealed. 

Kind of service wanted ascertained by symbol t<? 
which line connects. 

NOTE — If other than standard 1 6 c. p. incandescent lamps are desired, 
specifications should describe capacity of lamp to be used. 



I 



ELECTRICAL TABLES AND DATA 

TABLE LXXXIII 

Terminals. — George Cutter Co. 

Square Type, Cast. 

(See Figure 28.) 




Figure 28.— Terminals. 



Standard Dimensions, Inches 



Amps. 


Wire Size 


A 


B 


C 


D 


E 


F 


G 


30 


8 


i 


1 


i 


ft 


I 


ft 


ft 


50 


5 


ft 


1 


1 
5 


§ 


1 


3 ? 2 


ft 


75 


3 


f 


5 


ft 


\ 


H 


32 


A 


100 


1 


11 


I 


ft 


h 


u 


§2 


3*2 


150 


00 


if 


£ 


ft 


t 


11 


ft 


H 


175 


000 


1 


tf 


i 


ii 


li 


£ 


il 


200 


0000 


1ft 


1 


i 


it 


If 


ii 


si 


250 


300000 


1ft 


1 


ft 


ii 


l! 


ii 


M 


300 


350000 


If 


11 


i 


i 


2 


i 


M 


350 


400000 


u 


li 


ft 


ift 


21 


ft 


si 


400 * 


500000 


If 


li 


i 


ii 


2f 


it 


M 


500 


750000 


If 


If 


ft 


if 


2| ' 


ift 


32 


600 


1000000 


2 


11 


ft 


ift 


3 


ift 


32 


700 


1250000 


a* 


2 


i 


if 


3* 


ift 


h 


800 


1500000 


n 


2 


i 


2 


31 


u 


si 


1000 


2000000 


2| 


2i 


i 


21 


3S 


ii 


M 



238 



ELECTRICAL TABLES AND DATA 



Bound Type, Cast. 



Amps. 


Wire Size 


A 


B 


C 


D 


E 


F 


G 


30 


8 


A 


A 


i 


A 


f 


A 


A 


50 


5 


it 


1 


A 


f 


li 


& 


A 


75 


3 


if 


1 


A 


i 


li 


& 


& 


100 


1 


1A 


1 


A 


i 


If 


ii 


A 


150 


00 


1* 


1 


i 


5 


li 


A 


U 


175 


000 


1A 


n 


i 


ii 


li 


i 


il 


200 


0000 


li 


n 


i 


11 


If 


ii 


if 


250 


300000 


1A 


ii 


A 


If 


If 


ii 


II 


300 


350000 


li 


if 


A 


1 


2 


f 


ii 


350 


400000 


if 


ii 


A 


H 


2| 


if 


il 


400 


500000 


if 


n 


A 


H 


2| 


« 


ii 


500 


750000 


2* 


in 


i 


If 


3 


1A 


H 


600 


1000000 


2| 


2i 


f 


If 


3f 


1A 


U 


700 


1250000 


2| 


2i 


f 


If 


31 


1A 


il 


800 


1500000 


2f 


2i 


f 


2 


3| 


li 


ii 


1000 


2000000 


2f 
Right A 


21 
ngle 


f 
Type, 


2i 

Cast. 


4 


if 


li 


30 


8 


i 


f 


i 


A 


A 


A 


A 


50 


5 


f 


f 


i 


I 


f 


& 


A 


100 


1 


it 


1 


A 


} 


1 


ii 


& 


150 


00 


l 


i 


A 


f 


li 


A 


ii 


200 


0000 


l* 


1 


f 


it 


If 


if 


U 


300 


350000 


li 


li 


1 


l 


li 


f 


ii 


400 


500000 


H 


li 


f 


li 


If 


if 


ii 


600 


1000000 


2 


If 


A 


if 


2 


1A 


U 






Wrought Type. 










25- 50 


6 


A 


A 


& 


A 


i 


A 


A 


75-100 


3 


1 


A 


i 


f 


li 


i 


i 


150 





il 


» 


i 


i 


li 


f 


ii 


200 


000 


1A 


1 


i 


f 


If 


n 


f 


300 


300000 


li 


ii 


i 


f 


2 


f 


ii 



ELECTRICAL TABLES AND DATA 239 

Ammeter. — In choosing an ammeter one must con- 
sider whether it is for a. c, d. c. milli-amperes, full 
current, or shunt. Special instruments are made for 
each of these conditions; they are also made record- 
ing. 

Bond Tester. — This is an instrument made espe- 
cially for testing the conductivity of rail bonds and 
rails. 

Cable Testing Set. — Usually an instrument capable 
of locating faults in cables without cutting into the 
cable. 

Capacity Testing Sets. — A portable insulating and 
capacity testing set is made by the Leeds and North- 
rup Co. Other cable testing sets can also be used for 
this purpose. 

Current Transformers. — These instruments are 
used with a. c. circuits where large currents are to be 
measured ; also with wattmeters. 

Dynamometer. — This is a special form of galva- 
nometer which may be used for very accurate measure- 
ments of either voltage, current or watts. It can also 
be used for testing capacity and inductance and other 
tests for which volt or ammeters may be used. It is 
used mostly for a. c. work. 

Electrolytic Conductivity Apparatus. — The inter- 
nal resistance of batteries can be measured by means 
of the Wheatstone Bridge, but slight errors are pos- 
sible. To avoid these errors special apparatus has 
been constructed. 

Electrometer. — This is an instrument the operation 
of which is based on electric charges; used in lab- 
oratories for measuring difference of potentials. 

Frequency Meter. — Such instruments are used to 
determine the frequency of a.c. circuits. They may 
also be used as speed indicators. 



240 ELECTRICAL TABLES AND DATA 

Fault Finder. — This is a name given to certain 
special forms of testing instruments containing a bat- 
tery and resistances and arranged to facilitate testing. 

Galvanometer. — The galvanometer is a very deli- 
cate testing instrument and exists in a variety of 
forms. It is more delicate than the telephone re- 
ceiver for d. c, and where there is much noise, but 
for fluctuating currents the 'latter is more serviceable. 

Gauges. — "Wire gauges are used for measuring the 
diameters of wires, sheet metal, etc. See description 
under this heading. 

Ground Detectors. — Voltmeters and lamps are used 
for this purpose, as well as special electrostatic in- 
struments. 

Hydrometer. — This instrument is frequently re- 
quired in testing battery solutions. 

Illuminometer. — Illuminometers are of various 
kinds. Some of them are very simple and somewhat 
crude ; others are good photometers, a little more sim- 
ple and portable than the latter; usually calibrated 
in foot candles. 

Induction Standards. — Self and mutual induction 
standards are used in connection with the Wheatstone 
Bridge for comparing inductances. 

Iron Loss Watt and Voltmeters. — This is a special 
instrument made by the Westinghouse Co. for meas- 
uring the iron losses in transformers. 

Keys. — For high potential or precision work spe- 
cially constructed keys or switches are employed. 

Lamp and Scale. — For reflecting galvanometers a 
special lamp and scale are often required. 

Megger. — This is a trade name for a special testing 
set gotten out for general purposes. 

Meter Testing Sets. — These are special plugs and 
connections to facilitate the testing of wattmeters. 



ELECTRICAL TABLES AND DATA 241 

Micrometer. — This instrument answers the same 
purpose as the wire gauge, but is much more accurate 
and can be used for very accurate measurements. 

Multipliers. — These are resistances intended to be 
placed in series with voltmeters and which enable the 
voltmeters to be used for the measurement of higher 
voltages. 

Ohm-meters. — This is a simplified form of "Wheat- 
stone Bridge and is used for the same purposes; 
measuring resistances, detecting faults, etc. 

Oscillograph. — This is an instrument used for re- 
cording accurately the variation in the wave form of 
an alternating current or e. m. f . 

Permeability Meter. — The permeability meter is 
used for testing samples of iron as to their magnetic 
reluctance, or permeability. 

Phase Potation Indicator.— -This is an instrument 
used in determining direction of rotating field, or in 
connecting motors, etc. 

Photometer. — This device is used to measure inten- 
sity or degrees of illumination. Some photometers 
are cumbersome laboratory instruments; others are 
portable. 

Polarity Indicator. — This is an instrument used to 
determine the polarity of electric currents ; also made 
to determine the polarity of magnets. 

Potential Transformer. — This is a piece of ap- 
paratus used mostly for reducing the voltage by a 
fixed ratio so as to bring it within the range of in- 
struments. 

Power Factor Meter. — This piece of apparatus indi- 
cates the phase relation between the current and 
e. m. f . of the circuit, or generator, to which it is 
connected. 

Pyrometer. — The pyrometer is used for measuring 
heat. Some pyrometers depend upon electrical prin- 



242 ELECTRICAL TABLES AND DATA 

ciples for their action. They are sometimes used to 
determine the temperature of field coils. 

Resistances. — Separately mounted resistances are 
sometimes used in connection with the Wheatstone 
Bridge and other instruments to enlarge their scope. 

Rotating Standard. — This is a wattmeter in which 
a pointer moves rapidly, its movement being in pro- 
portion to the power consumed in the circuit at the 
time. It is especially designed to facilitate compari- 
son of meters with it. 

Sechameter. — This is an instrument used to measure 
coefficients of self-induction. 

Shunts. — These are used in connection with am- 
meters and so chosen that only a predetermined por- 
tion of the total current shall pass through the meter. 

Slide Wire Bridge. — This is a modification of the 
Wheatstone Bridge. 

Standardizing Set. — This is usually an arrange- 
ment of instruments of high grade which may be used 
to calibrate or standardize other instruments. 

Synchroscope. — This device indicates the phase dif- 
ference between two currents or e. m. f.'s to which it 
is connected. 

Tachometer. — This is a speed indicator, usually ar- 
ranged to be held against end of shaft. When fitted 
also with a stop watch, it is known as a tachoscope. 

Telefault. — This is a special type of testing instru- 
ment manufactured by Matthews & Bro., which en- 
ables certain tests to be made without cutting into the 
wires; can also be used for locating underground 
pipes. 

Telephone Receiver.— -The receiver is very sensitive 
to fluctuations in current strength and is much used 
for testing. With d. c. it gives only one click when 
current is switched on or off. Where there is much 
noise it is somewhat handicapped. 



ELECTRICAL TABLES AND DATA 243 

Thermometers. — These are used in testing ma- 
chinery and wires. Specially constructed instru- 
ments are mostly used. 

Voltameter. — An instrument measuring current 
strength by the amount of electrolyte decomposed. 

Volt -ammeter. — An instrument capable of measur- 
ing both current and voltage. 

Voltmeters. — They are used for measuring p. d. 
Not all are suitable for a. c. and d. c. ; some are elec- 
trostatic, some read in milli-volts and are recording. 

Wattmeters. — These are used for measuring power. 
Not all of them are suitable for d. c. and a. c. 

Wheat stone Bridge. — This is the best known of all 
electrical testing instruments. With it more tests 
can be made than with any other device. It is, how- 
ever, cumbersome and more difficult to handle than 
many of the other instruments. 

Thawing Water Pipes. — Special stepdown trans- 
formers are generally used for a. c. and must have at 
least 200 amperes capacity for the smaller pipes and 
should have much more for larger ones. Storage 
batteries have also been used. 

Theatres. — A full treatise on this subject is given 
in "Motion Picture Operation, Stage Electrics and 
Illusions." 

Arc Pockets. — These should be wired with no 
smaller than No. 6 ; switched at the board, and open 
at the bottom to prevent accumulation of dirt. Large 
theatres can well use pocket capacity for twenty arc 
lamps. The pockets should be arranged off stage, as 
close to the scenery as practicable. Each pocket 
usually contains four circuits. 

Auditorium. — Some auditoriums are thickly stud- 
ded with lamps, the purpose being to produce dec- 
orative effects. In such cases frosted lamps are 
advisable. The actual illumination may be brought 



244 ELECTRICAL -TABLES AND DATA 

about by arc lamps, or large chandeliers. Unless dec- 
orative effects are striven for, one 50-watt lamp will 
furnish enough illumination for twenty seats. From 
two to ten fan motors should be provided for, accord- 
ing to size of theatre. It is impossible to arrange a 
system of direct lighting in connection with which 
some of the lights will not be in the range of vision 
of part of the audience at least. If the expense is 
not prohibitive cove, or indirect lighting, would be 
very serviceable. Cove lighting is very useful to show 
off decorations about proscenium arch. 

Balcony. — In the balcony or gallery, provision for 
several arc lamps should be made. These should also 
be controllable from the main board. The ceilings in 
balconies are usually low, and lights must be kept 
well back to avoid range of vision of spectators. Use 
inverted lighting or small c.p. lamps kept well up 
at ceiling. Provide for fan motors. 

Blinding Lights. — This is a row of lights sometimes 
placed about proscenium arch, the purpose being to 
blind the audience for a few moments to permit a 
quick change of scenery. Lamps of high intrinsic 
brilliancy should be used. If decorations are of a 
light color, or emergency lights must be kept burning, 
the plan is not very successful. Never frost lamps 
used for this purpose. 

Borders. — From one to six borders, according to 
size and pretensions of house, are installed. Feed 
borders to center. Leave cables long enough so bor- 
ders may be lowered to within five feet of stage floor. 
Use slow-burning wire and arrange for color circuits. 
Borders should be suspended by wire rope • and in- 
sulated. Lamps are placed from six to twelve inch 
centers. The proportion of white and colored lamps 
is: two white, one red and one blue. Some borders 
are provided with a special circuit providing just 
light enough for rehearsals. 



ELECTRICAL TABLF-S AND DATA 245 

Bridges. — This is a name given to small galleries 
usually located at each side of proscenium and open- 
ing on stage side. Arc lamps are often operated 
from these bridges and arc pockets should be pro- 
vided. This is also a good place from which to con- 
nect stage chandeliers. 

Bunch Lights. — These lights are mostly fed out of 
stage pockets. The bunch circuits should be switched 
at the board, and some of them at least should be 
grouped with color circuits. Plugs used for incan- 
descent circuits on stage should not be interchange- 
able with arc lamp plu^s. 

Canopies. — Most theatres are equipped with cano- 
pies in front of house. These are often studded with 
lights. Arrange for low-wattage lamps and have 
them frosted. Arrange lamps to be out of weather. 
Sometimes provision is made for lamps in glass signs ; 
1320 watts will be allowed per circuit with these 
lights if they are properly wired for. 

Chandeliers. — Large chandeliers are often used in 
theatres. These should be hung so they may either 
be raised or lowered for renewal of lamps. 

Curtain. — In .large cities all theatres are fitted with 
heavy asbestos and steel curtains. These usually "re- 
quire motors to operate them. In some cities hy- 
draulic operation is required. In some cases the drop 
curtain is also operated by motor. 

Damper. — All good theatres, are provided with 
stage dampers which can be instantly opened in case 
of a fire on the stage. It is customary to hold the 
damper closed by an electromagnet, and to place a 
switch on each side of stage, said switch when opened 
releasing 1 the magnet and allowing the damper to 
open. 

Dressing Rooms. — Arrange dressing room illumina- 
tion without cords if possible. Provide circuit for 
^atiroa. Cover each lamp with a strong locked 



246 ELECTRICAL TABLES AND DATA 

guard. Arrange lights so that each side of face is 
illuminated by at least one lamp. Door switches are 
useful in dressing rooms. 

Emergency Lighting. — Every theatre should have 
an emergency lighting system capable of furnishing 
sufficient light for the audience to leave the house in 
case the main system fails. The emergency system 
should be entirely independent of the other lighting 
and in no way connected with it. It is customary to 
provide capacity for about one 25-watt lamp for each 
400 square feet of auditorium space. To this emer- 
gency system may also be connected a sufficient num- 
ber of exit lights to indicate doors and fire escapes. 
Allow no key sockets, fan motors, or other devices on 
emergency lighting circuits. 

Fire Alarm. — Provisions for fire alarm should be 
made. It is customary to connect the stage with the 
box office through a signal circuit that can be used 
for various purposes. 

Fire Pump. — This is provided to insure good pres- 
sure in case of fire. It must be wired for in the most 
substantial and reliable manner. 

Fly Floor. — This is that part of the gallery above 
stage, from which stage hands operate the curtains. 
A few lights only are needed, but they should be 
located convenient for men lounging between acts. 

Footlights. — These form the most important and 
effective part of the permanently located stage lights. 
They must be very carefully located so as to illumi- 
nate the lower part of stage without obstructing the 
view of the audience. Lights are generally studded 
as thickly as possible, and about half of them arranged 
for white and the other half divided into two colors. 
Galleries. — On these pockets for arc lamps, etc., are 
usually provided. 

Grid. — This is the name given to that part of the 
rigging loft to which sheaves, etc., operating curtains 



ELECTRICAL TABLES AND DATA 247 

and drops, are attached. Provide one light for each 
400 square feet. 

Lobby. — The lobby is usually very brilliantly illumi- 
nated, but the lights must be controlled by switches so 
that most of them may be turned out when the audi- 
ence is inside. Provide side outlets for picture illu- 
mination, etc. ; also for portable signs. 

Orchestra Lights. — The largest theatres have about 
100 outlets for orchestra lights. Less than twenty 
should not be considered in any first-class house. 
Place fuses on switchboard and arrange control so 
that one of the musicians can control lights in dark 
scenes. 

Program Board. — This is an arrangement of lights 
by which the next number on the program can be 
given the audience. A special outlet at each side of 
stage should be provided for it. Run large conduit, 
as many wires must be accommodated. 

Proscenium Side Lights. — These lights are arranged 
at each side of proscenium opening on stage side. 
Sometimes they are wired for three colors. 

Retiring Rooms. — These are usually wired in imita- 
tion of homes, cozy corner effects, table lamps, etc. 
Illuminate pictures on walls. 

Stage Switchboard. — The stage switchboard is 
usually located on right hand side of stage, facing 
the audience, and it is preferable to elevate it above 
stage level. The wiring of a good board should be 
divided into four parts, each independent of the 
others. All of the house lights should be controlled 
by one main switch; the footlights and all of the 
upper part of stage lighting by another, and the 
stage pockets by a third. In addition to this there 
should be a division to which lights that remain^ in 
use all of the time are connected. The stage lighting 
is again divided into three color groups, the white 



248 ELECTRICAL TABLES AND DATA 

lights being equal numerically to all of the colored 
lights. 

A list of the circuits which should be independent 
of all others and make up group four is given in the 
following : 

Dusting circuit. Fan motor circuit. 

Ventilating motor circuit. Curtain motor. 

Orchestra lights. Dressing room circuits. 

Program lights. Electric signs 

Fly floor lights. Rigging loft lights. 
Pilot lights. 

Fig. 29 shows a well-laid-out switchboard. All 
of the lights in the auditorium are controlled by 
switches shown in the upper right hand corner, and 
all of these are under control of the main switch. 
House lights are usually operated as a unit. 

The stage pockets are controlled by the bank of 
switches shown at F. Lights burning off of stage 
pockets are generally controlled by special operators 
or by actors, so that switches need not be so very 
convenient to switchboard operator. He must, how- 
ever, have them under his control. In the arrange- 
ment shown in Figure 29 the white lights predom- 
inate in the ratio of two to one, and are laid out in 
two groups, A and B. Both groups are controlled by 
the switch G. The switches A and B do not control 
the lights at all if the smaller throw-over switches at 
the right are thrown downward. A diagram of these 
switches is given in Figure 30, where the switches 
B and C are indicated. The object of the switches 
A and B is to help in quickly increasing or decreasing 
the illumination on the stage. If in the beginning of 
a certain scene, for instance, only a small quantity of 
light is wanted, the low illumination may be obtained 
by throwing the proper switches down ; the additional 



ELECTRICAL TABLES AND DATA • 24$ 

illumination which will be wanted a few minutes 
later may be prepared for by setting the other switches 
needed to the upward position and at the proper 



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Figure 29. — Stage Switchboard. 



moment closing switch B. In the same way, by a 
reversal of the process, the illumination may be 
instantly reduced. This feature is very valuable in 
many stage settings. To throw off all of the white 



250 ELECTRICAL TABLES AND DATA 

lights the switch C must be opened. The switches D 
and E are main switches controlling the colored 
lamps. All lamps of one color should be connected to 
one or the other of these switches. 

From these three groups of switches circuits extend 
into all borders, proscenium side lights and footlights, 
so that the color scheme may be carried out in any 
or all of them. 

The handles of all switches in the same row should 
be of the same height. Switches should be extra 
heavy. Dimmer handles should be located directly 
above switches controlling them. 




Figure 30. 



The fuses or switches controlling lights not usually 
manipulated by switchboard operator are generally 
worked into the vacant spaces between the groups 
mentioned above. 

All branch circuits are preferably located behind 
the board. This will allow of trouble being instantly 
rectified. * 

Transformers. — The transformer capacity which 
must be provided ranges from .20 to .80 percent of 
the connected load. 

The full load efficiency of transformers varies from 
.about 0.95 to 0.985. The smaller transformers are 



ELECTRICAL TABLES AND DATA 251 

less efficient than the larger, cost more per K. W., and 
give poorer regulation. Their installation is, however, 
much more economical in regard to wire. 

Transformers are properly rated in kilo-volt-am- 
peres (K.V.A.). They cannot accurately be rated in 
K. W. (although this term is often used), because the 
wattage depends upon the power factor, which is 
governed mainly by the load and line to which the 
transformer is connected. The efficiency of a trans- 
former can be found by dividing the output by the 
input. 

The polarity is generally such, that the current is 
entering the primary side at the same time it is leav- 
ing the secondary side corresponding to it. Oil 
cooled transformers are the most reliable, but should 
not be used where overflowing oil could do harm. 

The principal losses are the core or iron losses and 
the copper losses. The iron losses are the most impor- 
tant in transformers which are idle but connected 
the greater part of the time. Iron losses are continu- 
ous while the transformer is connected, whether it is 
delivering power or not. The copper losses take 
place only at time current is being used. The drop 
in voltage caused by them is proportional to the cur- 
rent, while the power loss is proportional to the 
square of the current. The iron losses are not of 
much importance at time of full load, but at this time 
the copper losses are the most disturbing. 
. The core losses can be ascertained by measuring the 
current delivered to the primary side while the sec- 
ondaries are open and noting the percentage of this 
to the full load current. 

The copper loss can be found by applying voltage 
enough to the primary wires to cause the full load 
current to flow in the secondary, which must be short- 
circuited. This power must be measured by a watt 
meter and the percentage to the total power noted. 



252 ELECTRICAL TABLES AND DATA 

Test all transformers for insulation before con- 
necting. 

All transformers should have their secondaries 
grounded, preferably at some neutral point. Shells 
of transformers should also be grounded. 

Tables for Determining the Most Economical Num- 
ber and Location of Transformers. — In a territory 
which has but few customers, and these somewhat 
scattered, each transformer constitutes a system by 
itself and is not connected to any other transformer. 
As the number of customers increases it becomes nec- 
essary either to extend the lines from one transformer 
or provide additional transformers and transfer part 
of the load to them. If the number of customers keeps 
on increasing, the mains from the various transformers 
soon meet, and may then be connected together, 
although, if transformers are far apart, there is no 
great advantage in this. Under these circumstances 
we have a number of transformers feeding a common 
line extending along a street. Finally, if the custom- 
ers still increase, or the load becomes greater, lines 
must be run on cross streets and these are connected 
to the others and we have a network of wires. In all 
three stages of the evolution of a secondary system of 
distribution, the determination of the most econom- 
ical arrangement of conductors and transformers is 
an important one. To keep the cost of wiring down 
to a minimum we must install a large number of small 
transformers. Small transformers are, however, more 
expensive in proportion to their capacity than large 
ones ; and full load, as well as all-day efficiency, is also 
much lower. 

The most economical arrangement from the point 
of view of first cost of installment is that with which 
the investment for wires plus the investment for 
transformers is a minimum. There are three differ- 
ent conditions under which it may be necessary to 



ELECTRICAL TABLES AND DATA 25G, 

determine the most advantageous location of trans- 
formers : The first is that where a secondary system 
exists at the terminus of a primary extension. Since 
the secondary wires usually carry about ten times as 
much current as the primary, it is generally econom- 
ical to extend the primary line to the center of the 
secondary system. If, for instance, the secondary 
system consists of a straight run, by doing this we 
may use a wire with four times the impedance that 
would be required if the transformer were at one end, 
or with a given wire, we may distribute four times the 
current for the same drop in voltage. 

These observations also hold good in case a number 
of transformers are to feed a continuous main. If 
we double the number of transformers, we quadruple 
the capacity of our wires or divide the drop by 4, 
provided, of course, they are evenly spaced through- 
out. 

When the secondary system finally reaches the net- 
work stage and, if we assume wires leading out from, 
each transformer in four directions with an equal 
load in each, we should be able to do with wire of; 
sixteen times the impedance of the first-considered 
case. There, is however, no great advantage in using 
such small wires, and at this stage large transformers 
are indicated. The whole network of wires is also* 
interconnected so that current from any one trans- 
former tends to distribute toward any part in which 
an area of low potential develops. 

In order to facilitate calculations concerning sec- 
ondary lines the following tables have been prepared.. 
By their use, if we assume even distribution of cur- 
rent, and even distance between distributing points, 
the drop at any part can be easily determined. In the 
lower table, LXXXVI, we have given the impedances 
for one ampere of 100 feet of line at 60 cycles and of 
various sizes of wire and at various separations. In 



254 ELECTRICAL TABLES AND DATA 

the upper table, LXXXIV, are given multipliers witl 
which, to multiply these impedances. It is assumed 
that the secondary line extends over a certain number 
of poles, and that at each of these poles a certain num- 
ber of amperes are taken off. In order to use this table 
we select the horizontal line pertaining to the numbei 
of poles covered by the line, and in it select the num- 
ber found where the vertical line pertaining to the 
pole at which we wish to determine the drop, crosses 
it. Multiplying this number by the current assumed 
to be taken off at each pole and by the impedance 
of the wire, we obtain the drop in voltage at this 
pole. 

Example : "We have a line extending over six poles 
(100 feet apart) and wish to find the drop at the third 
pole. We find the number 15 where the two lines 
cross ; our wire is No. 1 and the separation 36 inches 
while the current at each pole is 5 amperes; we have 
then for our drop 15x0.036x5= 2.7 volts. 

In case we wish to determine the smallest wire that 
can be used under similar circumstances or conditions, 
we use the formula 

IK 

in which Z is the impedance of the wire to be used 
V the volts to be lost, I the current and K a number 
selected from the table as explained above. 

y 

Values of -7-=: have been calculated for all of the 
1 K 

figures given in Table L^tXXIV, and in order to fine 
the smallest wire to deliver any amperage considered 
over any number of poles given, and at the desired 
loss, it is but necessary to follow the horizontal line 
pertaining to the proper constant K until it crosses 



ELECTRICAL TABLES AND DATA 255 

the vertical line pertaining to the amperes to be trans- 
mitted, and at this place we find the impedance of 
the wire, which will give us the drop of 2.7 volts. By 
referring the impedance to the table of impedances 
,we can then select the proper size of wire. These 
tables enable us to make trial calculations very rap- 
idly, and we can thus easily determine the most 
economical arrangement of conductors and trans- 
formers. 

Example : Suppose we have twelve poles spaced 
100 feet apart, and at each pole 5 amperes are to be 
used, While the drop must nowhere be greater than 
2.2 volts. Is it cheaper to feed this line with one large 
transformer or with two small ones? Placing the 
large transformer at about the center, we have six 
poles on one side and five on the other. In table 
LXXXIV for the sixth pole we find the constant 21, 
and in table LXXXV, where the line pertaining to 
this constant crosses with that pertaining to 5 amperes, 
we find the impedance 0.021. Looking up table 
LXXXVI for a corresponding impedance under 12- 
inch separation, we find 0.022 as the nearest, and that 
a 0000 wire is needed to come that near to our purpose. 
On the other side of the transformer we have only 
five poles, and the constant for this is 15, which in 
the same way we find requires an impedance of 0.029 
or a No. wire. Making the calculations for two trans- 
formers, and for a continuous main, we may use the 
constant for the third pole, which is 6. Looking this 
up as before, we find an impedance of 0.07, which 
indicates a No. 5 wire continuous main for us. In 
order to find which is the cheapest we must now bal- 
ance 1,100 feet of No. 5 wire and two 30-ampere 
transformers against 60.0 feet of 0000 wire plus 500' 
feet of No. 0, plus one 60-ampere transformer. 

Tables for calculating the most economical arrange- 
ment of transformers and conductors. 



256 ELECTRICAL TABLES AND DAT 

TABLE LXXXIV 

Number of poles Transformer pole not counted, 

covered by line 1st Pole 2nd 3rd 4th 5th 6th 

1 1 

2 2 3 

3 3 5 6 

4 4 7 9 10 

5 5 9 12 14 15 

6 6 11 15 18 20 21 

TABLE LXXXV 

V 
Showing Values of j= 

Con- 
stants Amperes 
K 123456789 10 12 15 

1 2.20 1.10 .733 .550 .440 .367 .314 .275 .244 .220 .183 .147 

2 1.10 .550 .366 .275 .220 .183 .157 .138 .122 .110 .091 .073 

3 .733 .366 .244 .183 .147 .122 .104 .092 .081 .073 .061 .049 

4 .550 .275 .183 .137 .110 .092 .078 .069 .061 .055 .046 .037 

5 .440 .220 .146 .110 .088 .073 .063 .055 .049 .044 .037 .029 

6 .366 .183 .122 .092 .073 .061 .052 .046 .041 .037 .030 .024 

7 .314 .157 .105 .079 .063 .052 .045 .039 .035 .031 .026 .021 
9 .244 .122 .081 .061 .049 .041 .035 .031 .027 .024 .020 .016 

11 .200 .100 .067 .050 .040 .033 .029 .025 .022 .020 .017 .013 

12 .183 .092 .061 .046 .037 .031 .026 .023 .020 .018 .015 .012 , 

14 .157 .078 .052 .039 .032 .026 .022 .020 .018 .016 .013 .010 I 

15 .147 .074 .049 .037 .029 .024 .021 .018 ,016 .015 .012 .010 
18 .123 .061 .041 .031 .025 .021 .018 .016 .014 .012 .010 .009 

20 .110 .055 .037 .028 .022 .017 .016 .014 .012 .011 .009 .007 

21 .105 .052 .035 .027 .021 .017 .015 .013 .012 .010 .009 .007 

TABLE LXXXVI 

Showing Impedance Per Bun of 100 Feet; 60 Cycles. 
Separation in Inches. Separation in Inches. 

B.&S. i 6 12 24 36 B. & S. $ 6 12 24 36 
8 .126 .127 .128 .128 .128 1 .026 .031 .033 .035 .036 

6 .081 .0S2 .083 .083 .084 .021 .027 .029 .031 .033 

5 .066 .068 .069 .070 .071 00 .017 .023 .026 .028 .030 
4 .051 .054 .055 .056 .057 000 .014 .021 .024 .026 .028 
3 .041 .044 .046 .047 .048 0000 .011 .019 .022 .025 .027 
2 .032 .038 .040 .041 



^ 



ELECTRICAL TABLES AND DATA 257 

An inspection of table LXXXVII will show that 
large transformers have a much higher all-day effi- 
ciency than small ones; for instance, by placing one 
4-K.W. transformer in place of four of 1 K.W.'s, we 
raise the efficiency (assuming the full load to be used 
three hours per day) from .84 to .91. In addition to 
this we also gain some in capacity, for the greater the 
number of customers connected to a transformer the 
greater will be the diversity factor. If we have a 
large number of small residences connected to one 
transformer, we need provide only about one-fourth 
the capacity of the connected load, whereas if we 
have one transformer for each customer we should be 
called upon for nearly the whole connected capacity. 
This gain in capacity comes in to such a marked 
extent only as long as we are dealing with trans- 
formers which are about fully loaded by one cus- 
tomer. As soon as the number of customers on any 
transformer reaches about twenty, they can be served 
with a transformer capacity which a larger number 
will not materially improve. A transformer capacity 
of one-fourth of the connected load will be sufficient 
for residence or flat lighting, but for stores, churches, 
and theatres a special study should be made as to 
what the maximum load of each is, and whether they 
are likely to occur at the same time. 

The use of larger transformers effects a saving in 
cost of transformers and in operating expenses, but 
entails a greater outlay for conductors, and to find 
which is the more economical we must balance the 
increased cost against the saving, and the most eco- 
nomical arrangement will be that in connection with 
which the value of the energy lost equals the interest 
on the investment of capital that must be made to 
save it. This must be found by trial calculations, and 
the various tables given will facilitate the calculations. 
It will, however, seldom be necessary to make such 



258 



ELECTRICAL TABLES AND DATA 



calculations, for in the first place the regulation of 
incandescent lamps limits us to a drop of about 2 
volts, which alone requires the use of comparatively- 
large wires; in the second place very low efficiency 
comes in only where the transformers are idle a 
large part of the time. This condition, even with low 
efficiency, causes only a nominal loss of power. 



TABLE LXXXVII 

Table Showing All Day Efficiency of Various Commercial 
Sizes of Transformers Used for Various Hours Per Day. 

Equivalent Full Load Hours Per Day. 



K.W. 


1 


2 


3 


6 


9 


12 


18 


24 


1 


66 


.78 


.84 


.89 


.92 


.93 


.94 


.96 


U 


70 


.81 


.86 


.90 


.93 


.94 


.96 


.96 


2 


72 


.84 


.88 


.93 


.94 


.95 


.96 


.96 


3 


77 


.86 


.90 


.94 


.95 


.96 


.96 


.97 


4 


79 


.87 


.91 


.94 


.95 


.96 


.96 


.97 


5 


81 


.88 


.92 


.95 


.95 


.96 


.96 


.97 


n 


82 


.90 


.92 


.95 


.96 


.97 


.97 


.97 


10 


83 


.90 


.93 


.96 


.96 


.97 


.97 


.97 


15 


85 


.91 


.93 


.96 


.97 


.97 


.97 


.98 


20 


86 


.91 


.94 


.96 


.97 


.97 


.97 


.98 


25 


87 


.92 


.94 


.96 


.97 


.97 


.97 


.98 


30 


87 


.93 


.95 


.96 


.97 


.97 


.97 


.98 


40 


88 


.93 


.95 


.96 


.97 


.97 


.97 


.98 


50 


89 


.94 


.96 


.97 


.98 


.98 


.98 


.98 



Trolley Lines. — Trolley wires range in size from 
to 0000 ; No. is seldom used and 00 and 0000 are 
the most used. 

Standard voltages d-c. are 600 and 1,200 ; a-c, 3,300, 
6,600, and 11,000. A trolley system usually consists 
of feeders, trolley, and track return. The track return 
is often reinforced with negative feeders, and negative 
boosters are also used. (See also Electrolysis.) 

The height of trolleys ranges from about 15 to 22 
feet above the street; 22 feet is about the minimum 
allowed above tracks. 



ELECTRICAL TABLES AND DATA 259 

Trolley sections range from a few hundred yards 
to several miles in length; heavy traffic zones are 
usually fitted with short sections, Poles range from 
30 to 40 feet in length, and wooden poles usually 
have 7-inch tops. The rake of poles varies from 
4 to 12 inches, according to nature of soil. 

There are various ways of trolley wire connections. 

The trolley may be run alone ; it may be reinforced 
by feeders, trolley and feeders being in parallel, or 





























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Figure 31. — Train Sheet. 

it may be cut in sections, each section being fed by 
f its own feeder. Alternating current systems do not 
usually have any secondary feeders. The drop allowed 
in d-c. systems ranges from 10 to 25 per cent ; for a-c. 
systems it is 5 to 10 per cent. 

The current used at any point can be approximately 
determined by use of the "train sheet" illustrated in 
Figure 31. The height of the figure represents the 
length of the road or of any part of it to be considered. 
The width of it may represent the length of time 
during which the load is to be determined. 

For each car, or train, entering a section of trolley, 
draw a line beginning with the time the car enters 



ELECTRICAL TABLES AND DATA 



the section at the bottom and to meet the time point 
at the top at which it leaves that section. Draw lines 
beginning at the top. of the figure in the same manner 
for all cars moving in the opposite direction. These 
lines will then cross, and to find the load on this 
section at any desired time, it is only necessary to 
draw an ordinate such as 1 at that point and count the 
number of car lines this crosses. This will give the 
number of cars fed over this section of trolley at that 
time, and the maximum current used can be easily 
determined. 

TABLE LXXXIX 

Table Showing Drop in Voltage Per 100 Amperes for Distance 
Given. 



Feet 

1,000 2,000 3,000 4,000 

11.9 23.8 35.7 47.6 

9.44 18.9 28.3 37.8 

7.48 15.0 22.4 29.9 

5.94 11.9 17.8 23.8 



Miles 
12 3 4 

62.8 125.6 188.4 251 
49.8 99.6 149. 199 
39.5 79.0 118. 158 
31.4 62.8 71.4 126 



5 
314 
249 
198 
157 



B.&S. 


00 
000 
0000 
CM. 

500000 2.513 5.0 7.5 10.5 13.26 26.5 39.8 53.0 66.3 
1000000 1.256 2.51 3.7 5.0 6.63 13.3 19.9 26.6 33.2 
2000000 0.628 1.26 1.88 2.51 3.31 6.6 10.0 13.2 16.6 
3000000 0.419 0.84 1.26 1.67 2.21 4.4 
4000000 0.315 0.63 0.95 1.26 1.65 3.3 



D. C. Only. 



6.6 
5.0 

5000000 0.251 0.50 0.75 1.00 1.33 2.65 4.0 



6.6 
5.3 



11.0 
8.3 
6.6 



TABLE LXXXX 



Table Showing P.D. on Eeturn for Distances Above. 



Wt. of Rails 

Per Yard. 

2 Rails Used. 

40 

45 

50 

60 

70 

80 

90 

100 

110 



1.23 2.46 3.69 4.92 ( 

1.09 2.18 3.27 4.36 5.8 11, 

0.98 1.96 2.94 3.92 5.2 10, 

0.81 1.62 2.43 3.24 4.3 

0.70 1.40 2.10 2.80 3.7 

0.61 1.22 1.83 2.44 3.2 

0.55 1.10 1.65 2:20 2.9 

0.49 0.98 1.47 1.96 2.6 

0.45 0.90 1.35 1.80 2.4 



13.0 


19.5 


26.0 


32.5 


L1.6 


17.4 


23.2 


29.0 


L0.4 


15.6 


20.8 


26.0 


8.6 


12.9 


17.2 


■21.5 


7.4 


11.1 


14.8 


18.5 


6.4 


9.6 


12.8 


16.0 


5.8 


8.7 


11.6 


14.5 


5.2 


7.8 


10.4 


13.0 


4.8 


7.2 


9.6 


12.0 



ELECTRICAL TABLES AND DATA 261 

The copper loss calculations are based on resistivity of hard 
drawn copper at 65° C 149° F. 

Eails are supposed to be standard and of specific resistance 
of 10 times that of copper. 

The losses in return circuit will be less than indicated 
because part of current returns through piping and earth. 

The combined drop in conductors and rails in parallel is 



equal to — +-tj- + -p- where d, d*, d2, etc., represent the- 

drop in the different conductors. 

The impedance of the rails at 25 cycles is said to be from 
6 to 7 times as high as the ohmic resistance. 

Impedance of trolley=1.5 times ohmic resistance. 



Tables LXXXIX and LXXXX have been especially 
prepared to facilitate calculations concerning drop in 
trolley circuits. Every trolley circuit consists of three 
elements: trolley proper, its feeders and the track 
return, and in order to effect distribution econom- 
ically, it is necessary to consider all of these sepa- 
rately. 

The upper part of table LXXXIX gives the drop- 
in voltage caused by the trolley proper, and the lower 
part that caused by feeders, either overhead to rein- 
force trolley or underground to help out track rails,, 
and table LXXXX the drop caused by the iron rails. 
The calculations have not been carried out for a-c. be- 
cause the circuits used for this method of transmission 
differ materially from d-c. systems. In a-c. systems 
the ground return may be considered as made up of 
a number of comparatively short sections, the current 
returning not to the central station but to its trans- 
former. This is also true of the trolley. With energy 
distributed at 25 cycles, the drop caused by the rails, 
will be about 6.5 times as great as for d-c. and that 
in the trolley about 1.5 times. The drop caused by 



262 ELECTRICAL TABLES AND DATA 

trolley and feeders, when they are in parallel, is 
equal to the reciprocal of the sum of the reciprocals 
of their lines. This is also the case with track rails 
and their reinforcement. 

As far as these are used in series the various losses 
must be added. 

The use of the tables can perhaps be best made 
clear by an example. 

Example : The train sheet shows that 1,200 am- 
peres will be required on a certain section of trolley 
one mile long and fed in the center by a feeder two 
miles long. The loss at far end of trolley must not 
exceed 15 per cent of the voltage, which is 600. The 
rails weigh 100 lbs. per yard, and the difference in 
potential between any two points must not exceed 
5 volts. What size of feeder and reinforcement of 
track rails will be necessary? 

Table LXXXIX shows that a 0000 trolley wire will 
cause a drop of 31.4 volts in one mile per 100 amperes. 
Our trolley is fed in the center and must be con- 
sidered one-half mile long; each half carries half of 
the current, viz., 600 amperes; therefore, the drop 
caused by a 0000 trolley will be six times the drop in 
half a mile, or, according to our table, 94.2 volts. 
This alone is more than 15 per cent of our voltage, 
600, hence we must divide our trolley into shorter 
sections. Making two sections out of the same length, 
or feeding it in two places, will give us a loss equal 
to 300 amperes for one-fourth mile, or just one- 
fourth of what we had before, viz., 23.6 volts lost in 
trolley. 

We have next to deal with the size of feeder, and 
are allowed a loss of slightly over 60 volts in it. The 
loss in feeders two miles long is given in table 
LXXXX, and we may use any feeder the loss of ; 
which, multiplied by 12, does not exceed 67 volts. 



ELECTRICAL TABLES AND DATA 263 

12 times 6.6 equals 79.2, and is the loss caused by a 
2,000,000-cm. cable. This we must not use, but the 
next larger one will give us a loss of only 52.8, and 
this, added to the trolley loss, makes a total of 76.4 
volts. If it is desired to lose the full 90 volts a 
smaller trolley wire may now be considered. 

The loss in one mile of 100-lb. track is 2.6 volts 
per 100 amperes, which makes 31.2 for 1200; a 
5,000,000-cm. cable causes a drop of twelve times 
1.33, or 15.96 volts. The drop caused by both in 
parallel will be the reciprocal of the sum of the 
reciprocals. By the table of reciprocals we find the 
reciprocal of 31.2 is, roughly, 0.032051, and that of 
15.96 is 0.062500. Adding these, we have 0.094, ap- 
proximately. The number corresponding to this from 
the same table is 10.6, which is more than two times 
too high. Let us now consider the use of two 5,000,- 
000 cables. The drop in the cables will be just half 
of what it was before, or about 8. The reciprocal of 
8 is 0.01250; this added to 0.032 gives us 0.157, and 
the number corresponding to it is about 6.4. This is 
still above what we require, but it must be borne in 
mind that not all of the current returns over the rails 
and negative feeders, hence, this will give us about 
the right p.d. The loss in trolley lines, track, and 
feeders can be lessened very much by increasing the 
number of substations from which they are fed, and 
the most economical arrangement can be determined 
by the same calculations laid out for locating trans- 
formers. 

Underground Construction. — Underground con- 
ductors are usually lead encased and as the lead is 
not very strong it is best to run the conductors in some 
form of conduit which protects them and facilitates 
removal in case of trouble. These conduits usually 
consist of some kind of clay, concrete or fiber, and 
their heat conductivity is generally not as good as 



264 ELECTRICAL TABLES AND DATA 

that of moist earth. Conduits arranged as shown in 
Figure 32 carry away more heat than those shown 
at Figure 33, but if there are many of them they also 
require more trench area. 

All conduits should be arranged to drain, and at 
suitable intervals should be provided with splicing 
chambers. If space between them is to be filled 
with concrete they must be anchored to prevent 
floating. 




The following tables and information is taken from 
Handbook No. 17 of the Standard Underground 
Cable Co. (Copyright by Standard Underground 
Cable Co., 1906). 

Recommended Current Carrying Capacities for 
Cables, and Watts Lost per Foot, for each of four 
equally loaded single conductor paper insulated lead 
covered cables, installed in adjacent ducts in the 
usual type of conduit system where the initial tem- 
perature does not exceed 70° F. (21.1° C), the 
maximum safe temperature for continuous operation 
being taken as 150° F. (65.5° C). 



ELECTRICAL TABLES AND DATA 



265 



TABLE LXXXXI 



Size 
B. &S. 


Safe 
Cur- 
rent 
in 
Amp. 


Watts 
Lost 
Per 
Ft. at 
150° F, 


Size 
B. &S. 
or 
, C. M. 


Safe 
Cur- 
rent 

in 
Amp. 


Watts 
Lost 
Per 
Ft. at 
150° F. 


Size 

Circular 

Mils. 


Safe 
Cur- 
rent 

in 
Amp. 


Watts 

Lost 

Per 

Ft. at 

150° F. 


14 


18 


0.97 


2 


125 


2.77 


900000 


650 


5.71 


13 


21 


1.03 


7 


146 


3.00 


1000000 


695 


5.86 


12 


24 


1.09 





168 


3.23 


1100000 


740 


6.01 


11 


29 


1.15 


00 


195 


3.46 


1200000 


780 


6.13 


10 


33 


1.25 


000 


225 


3.69 


1300000 


820 


6.25 


9 


38 


1.39 


0000 


260 


3.92 


1400000 


857 


6.37 


8 


45 


1.53 


300000 


323 


4.22 


1500000 


895 


6.49 


7 


53 


1.67 


400000 


390 


4.61 


1600000 


933 


6.61 


6 


64 


1.85 


500000 


450 


4.91 


1700000 


970 


6.73 


5 


76 


2.08 


600000 


505 


5.16 


1800000 


1010 


6.85 


4 


91 


2.31 


700000 


558 


5.36 


1900000 


1045 


6.97 


3 


108 


2.54 


800000 


607 


5.56 


2000000 


1085 


7.09 



Assuming that unity (1.00) represents the carrying 
capacity of single-conductor cables, the capacity of 
multi-conductor cables would be given by the fol- 
lowing : 

2 Cond., flat or round form, 0.87 ; concentric form, 
0.79. 

3 Cond., triplex form, 0.75; concentric form, 0.60. 
The following experiment on duplex concentric 

cable of 525,000 cm. indicates clearly the danger in 
subjecting this type of cable to heavy overloads of 
even short duration. The cable was first heated up 
by a current of 440 amperes for five hours. An over- 
load of 50 per cent was then applied, the results in 
degrees Fahrenheit above the surrounding air being 
as follows : 



Time from start min. 15 min. 30 min. 45 min. 60 min. 90 min. 

Inner condr.. . 70° 84° 98° 111 123° 142° 

Outer condr... 55° 65° 76° 85° 94° 108° 

Lead cover... 31° 35° 40° 45° 49° 57° 



266 ELECTRICAL TABLES AND DATA 

As it is the final temperature reached which really 
affects the carrying capacity, the initial temperature 
of surrounding media must be taken into account. 
If, for instance, the conduit system parallels steam 
or hot water mains, the temperature of 150 F., which 
we have assumed in the table to be the maximum for 
safe continuous work on cables, will be reached with 
lower values of current than would otherwise be the 
case; and as 70 is the actual temperature we have 
assumed to exist in the surrounding medium prior to 
loading the cables, any increase over 70 must be 
compensated for by reducing the current. 

For rough calculations it will be safe to use the 
following multipliers to reduce the current carrying 
capacity given in table LXXXXI to the proper value 
for the corresponding initial temperatures. 

Initial temp. F. 70° 80° 90° 100° 110° 120° 130° 140° 150° 
Multipliers ...1.00 0.93 0.86 0.78 0.70 0.60 0.48 0.34 0.00 

When a number of loaded cables are operating in 
close proximity to one another, the heat from one 
radiates, or is carried by conduction, to each of the 
others, and all are raised in temperature beyond what 
would have resulted had only a single cable been in 
operation. And if the cables occupy adjacent ducts 
in a conduit system of approximately square cross- 
section laid in the usual way, the centrally located 
cable or the one just above the center in large installa- 
tions (A in Figure 32) will reach the highest tem- 
perature. This is equivalent to saying that its cur- 
rent carrying capacity is reduced and while this re- 
duction does not amount to more than 12 per cent 
(as compared with the cable most favorably located, 
D, Figure 32) in the duct arrangement given it may 
easily assume much greater proportions where a large 
number of cables are massed together. 



ELECTRICAL TABLES AND DATA 



Assuming that not more than twelve cables, ar- 
ranged as shown in Figure 32, can be used, the aver- 
age carrying capacity may be taken as the criterion 
for proper size of conductor, and for cables of a 
given type and size the carrying capacities of all 
cables, even though placed in adjacent ducts, will be 
represented by the following figures, taking unity as 
the average carrying capacity of four cables. (See 
Table LXXXXI.) 

Number of cables 2 4 6 8 10 12 

Multiplier 1.16 1.00 0.88 0.79 0.71 0.63 

Recommended Power Carrying Capacity in Kilo- 
watts of Delivered Energy. — The tables below are 
based on the carrying capacities of cables as given in 
Table LXXXXI. A power factor of unity was used 
in the calculations and hence the values found in the 
lower table are correct for direct current. For alter- 
nating current the kilowatts given must be multiplied 
by the power factor of the delivered load. 

Units. — Synopsis of units and symbols in general 
use. 

Defining Equation 



Unit 


Name 


Sym- 
bol 


Direct 
Current 


Alternating 
Current 


Electromotiv 

force 
Current 


e 

Volt 
Ampere 


E, e 
I, i 


IE 
E--R 


IZ 
E-hZ 


Resistance 
Power 


Ohm 
Watt 


R, r 
P 


E-f-I 

EI 


VZ2 — X2 

E I X p. f . 


Impedance 


Ohm 


Z, z 




VR 2 +X2 


Reactance 
Inductance 

Capacity 
Quantity 


Ohm 
Henry 

Farad 
Coulomb 


X, x 

L, 1 
C, c 

Q, q 


fc + I 
Q-s-E 

I X time 


VZ2 — R2 

I X time 


Admittance 


Mho 


Y, y 




I _ z = V G2 -f B2 


Conductance 


Mho 


<*, g 


I-r-B 


R-^-Z2= VY2 — B 


Su'sceptance 


Mho 


B, b 




X — Z2 = y Y2 — G2 



ELECTRICAL TABLES AND DATA 



TABLE LXXXXTI 



Size in 


inn 


>e v_/on<_ 


lUCLUIj 


xnum- 


riiase 


^auies 






£. &S. 








Volts. 










1100 2 


200 330C 


L3200 


22000 








Kilo-Watts 










6 


92 


183 


275 


333 


549 


915 


1098 


1831 


5 


109 


217 


326 


395 


652 


1087 


1304 


2174 


4 


130 


260 


390 


473 


781 


1301 


1562 


2603 


3 


154 


309 


463 


562 


927 


1544 


1854 


3089 


2 


179 


358 


536 


650 1073 


1788 


2145 


3575 


1 


209 


418 


626 


759 1253 


2088 


2506 


4176 





240 


481 


721 


874 1442 


2402 


2884 


4805 


00 


279 


558 


836 1014 1674 


2788 


3347 


5577 


000 


322 


644 


965 1172 1931 


3217 


3862 


6435 


0000 


372 


744 1115 1352 2 


231 


3717 


4462 


7435 


:250000 


413 


827 ] 


240 1 


.503 2 


480 


4132 


4960 


8264 




Single Conductor 


Cables, 


A. C. 


or D. 


C. 










Volts. 












125 


250 


500 


1100 


2200 


3300 


6600 


11000 








Kilo-Watts 


. 








6 


8.0 


16.0 


32 


70 


141 


211 


422 


704 


5 


9.5 


19.0 


38 


84 


167 


251 


502 


836 


4 


11.4 


22.8 


45 


100 


200 


300 


601 


•1001 


3 


13.5 


27.0 


54 


119 


238 


356 


713 


1188 


2 


15.6 


31.2 


62 


138 


275 


413 


825 


1375 


1 


18.3 


36.5 


73 


161 


321 


482 


964 


1606 





21.0 


42.0 


84 


185 


370 


554 


1109 


1848 


00 


24.4 


48.8 


97 


215 


429 


644 


1287 


2145 


000 


28.1 


56.3 


113 


248 


495 


743 


1485 


2475 


0000 


32.5 


65.0 


130 


286 


572 


858 


1716 


2860 


300000 


40.4 


80.8 


162 


355 


711 


1066 


2132 


3553 


400000 


48.8 


97.5 


195 


429 


858 


1287 


2574 


4290 


500000 


56.3 


112.5 


225 


495 


990 


1485 


2970 


4950 


600000 


63.1 


126.3 


253 


556 


1111 


1667 


3333 


5555 


700000 


69.8 


139.5 


279 


614 


1228 


1841 


3683 


6138 


800000 


75.9 


151.8 


304 


668 


1335 


2003 


4006 


6677 


900000 


81.3 


162.5 


325 


715 


1430 


2145 


4290 


. 7150 


1000000 


86.9 


173.8 


348 


764 


1529 


2294 


4587 


7645 


1100000 


92.5 


185.0 


370 


814 


1628 


2442 


4884 


8140 


1200000 


97.5 


195.0 


390 


858 


1716 


2574 


5148 


8580 


1400000 


107.1 


214.3 


429 


943 


1S85 


2828 


5656 


9427 


1500000 


111.9 


223.8 


448 


985 


1969 


2954 


5907 


9845 


1600000 


116.6 


233.3 


467 


1026 


2053 


3079 


6158 


10263 


1700000 


121.3 


242.5 


485 


1067 


2134 


3201 


6402 


10670 


1800000 


126.3 


252.5 


505 


1111 


2222 


3333 


6666 


11110 


2000000 


135.6 


271.3 


543 


1194 


2387 


3581 


7161 


11935 



ELECTRICAL TABLES AND DATA 269 

Ventilation. — Ventilation for the purpose of pro- 
viding a certain quantity of fresh air to occupants of 
rooms or shops requires the apparatus to be in use 
continuously while the rooms are occupied, regardless 
of temperature. Where it is provided mainly to carry 
off surplus heat, it is used only in warm weather. The 
capacity in such cases must be sufficient to take care 
of the hottest weather. 

The quantity of air moved by any fan varies 
directly as the speed, but the power required to run 
the fan varies as the cube of the speed. The net 
result is that the cost of moving different volumes of 
air by any given fan varies about as the square of the 
speed at which the fan must operate to move it. This 
is the theoretical relation, but this is somewhat dis- 
turbed by the difference in efficiency of large and 
small motors operating at various speeds. Owing to 
the above facts it is often a difficult task to decide 
whether it is more profitable to install a small, cheap 
fan and run it at a high rate of speed, or to provide 
a more expensive one and operate it at a lower cost 
per unit of air moved. Which is the more profitable 
in the long run depends upon the number of hours 
per year the fan is to be used at its various speeds. 
In any case the most economical ventilator will be the 
one in connection with which the cost of energy saved 
per year will equal the interest charge upon the in- 
vestment of capital necessary to provide it in place of 
the cheapest fan which can do the work. The follow- 
ing tables are taken from publications of the American 
Blower Co. and give all the necessary data for com- 
parison of various fans. In order to find the most 
economical fan select the smallest fan capable of mov- 
ing the requisite amount of air and note the K. W. 
necessary to run it (divide H. P. given by 1.3). Next 
select some larger fan and note the K. W. necessary 
to move the same volume of air with this fan and sub- 



270 ELECTRICAL TABLES AND DATA 

tract it from the first. The next step is to find the 
value of the annual saving, by multiplying the number 
of hours per year this power is used by the rate per 
K. W. Having found this, if we divide it by the rate 
of interest applicable, we shall obtain the sum of 
money which we can afford to spend to substitute 
this fan in place of the smallest one we were consid- 
ering. The rate of interest by which we must divide 
is determined by the number of years the installation 
is to remain in use and is as follows : 

One year, 1.06 per cent ; 2 years, .57 ; 3 years, .40 ; 
4 years, .32 ; 5 years, .27 ; 6 years, .24 ; 7 years, .21J ; 
8 years, .20; and 9 years, .18J. 

"We have now the following formula by which we 
can determine the amount of capital which can with 
profit be invested in a larger fan: 

n K. W. -k.w.xhxr 

c= % "~ 

where C = capital to be invested; K. "W. - k. w. - the 
saving in energy per hour, and h and r = the number 
of hours per year and rate per K. W. hour of energy. 
In case the fan is used intermittently at various 
speeds the calculations should be made accordingly, 
since tlfe power required at high speeds is much 
greater than at low speeds. The capacity of a fan 
used only to provide a sufficient quantity of fresh air 
is best determined by allowing from 30 to 50 cubic 
feet of air per minute for each adult, and from 20 
to 35 for each child. In special places such as hos- 
pitals this quantity is often doubled. The maximum 
quantities given will secure ample ventilation for all 
ordinary persons. In public places such as toilet 
rooms, waiting rooms, etc., it is customary to require 
from three to six changes of air per hour. 



ELECTRICAL TABLES AND DATA 271 

TABLE LXXXXIII 

t( Ventura' ' Disc Ventilating Fans. 

General Capacity Table. — American Blower Co. 

Capacities, Speeds and Horse Powers with Unobstructed 
Inlet and Discharge. 

No. of Velocity of Air in Feet per Minute. 

Fan 600 900 1200 1500 1800 2100 

Cu. Ft. Per Min.. 950 1420 1895 2370 2840 3320 

3 Pres. Ins. W. G.. .0225 .055 .09 .1406 .2025 .2755 

E. P. M 625 980 1255 1565 1880 2190 

H. P 0097 .036 .079 .153 .265 .42 

C. F. M 1620 2430 3240 4050 4860 5670 

4 Pres. ins 0225 .055 .09 .1406 .2025 .2755 

E. P. M 470 735 945 1175 1410 1645 

H. P 0168 .062 .13 .262 .455 .72 

C. F. M 2500 3750 5000 6250 7500 8750 

5 Press. Ins 0225 .055 .09 .1406 .2025 .2755 

E. P. M 375 585 755 938 1125 1310 

H. P 026 .095 .207 .405 .701 1.10 

C. F. M 3560 5350 7125 8900 10700 12500 

6 Press. Ins 0225 .055 .09 .1406 .2025 .2755 

R. P. M 315 492 632 786 945 1100 

H. P 037 .136 .295 .575 1.00 1.59 

C. F. M 4S00 7200 9600 12000 14400 16800 

7 Press. Ins 0225 .055 .09 .1406 .2025 .2755 

E. P. M 288 419 537 669 803 936 

H. P 05 .182 .398 .776 1.345 2.13 

C. F. M 6250 9375 12500 15600 18750 21850 

8 Press. Ins 0225 .055 .09 .1406 .2025 .2755 

E. P. M 234 366 470 584 702 817 

H. P 065 .237 .516 1.01 1.75 2.77 

C. F. M 7875 11800 15700 19650 23600 27500 

9 Press. Ins 0225 .055 .09 .1406 .2025 .2755 

E. P. M... 209' 326 419 521 626 730 

H. P 082 .30 .65 1.27 2.20 3.48 



272 ELECTRICAL TABLES AND DATA 

TABLE LXXXXIV 

Capacities, Speeds and Horse Powers with Eesistance of 
Average Piping System. 

No. of Velocity of Air in Feet per Minute. 

Pan 600 900 1200 1500 1800 2100 

Cu. Ft. Per Min.. 950 1420 1895 2370 2840 3320 

8 Press. Ins. W. G.. .06 .15 .24 .37 .53 .73 

E. P. M 716 1075 1435 1790 2150 2510 

H. P 022 .085 .18 .34 .59 .93 

C. F. M 1620 2430 3240 4050 4860 5670 

4 Press. Ins 06 .15 .24 .37 .53 .73 

E. P. M 540 808 1075 1345 1615 1885 

H. P. 037 .14 .30 .58 1.00 1.59 

C. F. M 2500 3750 5000 6250 7500 8750 

5 Press. Ins...."... .06 .15 .24 .37 .53 .73 

E. P. M 430 644 860 1075 1288 1500 

H. P 057 .21 .46 .90 1.54 2.45 

C. F. M 3560 5350 7125 8900 10700 12500 

6 Press. Ins 06 .15 .24 .37 .53 .73 

E. P. M 361 540 720 900 10S0 1260 

H. P 082 .30 .65 1.27 2.20 3.50 

C. F. M 4800 7200 9600 12000 14400 16800 

7 Press. Ins 06 .15 .24 .37 .53 .73 

E. P. M 307 460 614 767 920 1075 

H. P 11 .40 .88 1.71 2.96 4.69 

C. F. M 6250 9375 12500 15600 18750 21850 

8 Press. Ins 06 .15 .24 .37 .53 .73 

E. P. M 268 402 535 670 803 940 

H. P 143 .53 1.14 2.23 3.85 6.10 

C. F. M 7875 11800 15700 19650 23600 27500 

9 Press. Ins 06 .15 .24 .37 .53 .73 

E. P. M 239 358 477 597 716 835 

II. P 18 .67 1.43 2.80 4.84 7.68 

Pressures noted are static pressures. 



ELECTRICAL TABLES AND DATA 273: 

Where it is desired to reduce temperature or remove: 
steam, etc., we must proceed to find the necessary 
capacity in another way. If we remove all of the 
heated air in a room and replace it with air from the 
outside in the same length of time required to heat it, 
we shall reduce the temperature by one-half the dif- 
ference between that of the air in the room and the air 
brought in. From this fact we can deduce the fol- 
lowing method for determining the amount of air 
which must be taken out of a room in order to lower 
its temperature by any desired amount. Before the 
room has attained its full temperature place one or 
more thermometers at representative locations and 
note the temperature rise for any convenient length of 
time, but be sure that you are observing the maximum 
or general temperature rise which is to be ventilated 
for. By providing ventilator capacity to exhaust alL 
of the air in the room one or more times in the same 
length of time in which the rise took place we shall, 
reduce it according to the following tabulation whick 
shows the number of degrees F. which the room tem- 
perature will be above the outside temperature with, 
the number of changes taking place as given at the 
left in column 0. The column is correct only when 
the room is so tightly closed that there is no natural 
ventilation. Under the other columns, headed by 
1, 2, 3, 4, and 5, are given the number of times the 
air must be changed to limit the temperature rise in 
room to the increases above the outside air as given 
in right hand section of table. Thus, if the increase 
in temperature allowed over the outside air is 30 
degrees and the air is naturally changing three times 
we must change it twelve times to limit the rise to 5 
degrees. 



ELECx'RICAL TABLES AND DATA 



TABLE LXXXXV 



Number of natural 



changes of air 








Increase in 


degrees F. 






assumed. 








above outside air. 






5 4 3 2 1 





5 


10 


15 20 


25 30 


35 


40 


10 8 6 4 2 


1 


2| 


5 


7* 10 


122 15 


m 


20 


15 12 9 6 3 


2 


U 


2i 


3| 5 


6* 71 


81 


10 


20 16 12 8 4 


3 


f 


if 


U H 


4i 5 


5f 


6§ 


25 20 15 10 5 


4 


f 


li 


1| 2* 


3* 3| 


4| 


5 



JKwZe. — Determine difference in temperature be- 
tween outer and inner air which is to be ventilated for, 
and trace down column headed by this temperature 
until the allowable temperature of inner over outer 
air is reached. Next estimate number of natural 
changes taking place during the time of previous test 
and in section of table at left headed by this number 
trace down to same horizontal line in which the per- 
missible temperature was found. At this point the 
necessary number of changes in air will be found. 
These changes must take place in the same length of 
time in which the temperature rise took place. 

If there is a temperature rise accompanied by nat- 
ural ventilation the reductions in temperature given in 
Table LXXXXV, column 0, can be obtained only by 
doubling the number of changes taking place dur- 
ing the time that the rise in temperature was going 
on. 

Suppose, for instance, that a certain temperature 
rise takes place in an hour while during the same time 
the air is naturally changing ten times. The starting 
of the ventilator, if of sufficient capacity, immediately 



ELECTRICAL TABLES AND DATA 275- 

ends all natural ventilation because every former out- 
let for air now becomes an inlet and all air passes 
through the fan. The number of changes which were 
naturally taking place now count for nothing and to 
reduce the temperature by one-half we must provide 
ten more changes per hour, i.e., change the air by 
means of the fan twenty times to obtain the effect of 
one change as given in column 0. Thus to find the 
number of changes necessary to obtain the effects given 
in the table in column we must use the formula 
c=(axb)+a, where c=the number of changes that 
must be made ; a = the number of natural changes tak- 
ing place, and b = the figure in column which corre- 
sponds to the desired rise above the outside air at the 
difference in temperature. 

Example. — The increase in temperature in a certain 
room is 10 degrees above that of the outside air and is 
to be limited to 2-J degrees; the dimensions of the 
room are 100 x 20 x 12, while the natural change of air 
is assumed to be about three times per hour. What 
must be the capacity of the ventilating fan ? Tracing 
down in Table LXXXXV under 10 degrees to where 
2J is found, and then in the horizontal line to the left, 
to column pertaining to three changes of air per hour, 
we find the number 9, which signifies that we must 
have capacity to change the air nine times per hour,, 
and since the room contains 24,000 cubic feet we must 
select a fan which can move 3,600 cubic feet per 
minute. 

Practical Hints. — Place ventilators at end of room 
opposite to where most of the air enters or so that all 
disagreeable air is nearest to the fan. Protect fan 
against wind blowing into it. Avoid noise by selecting 
large fans to operate at low speeds. Air in motion 
does not feel as warm as stationary air. It is best to 
provide a separate fan for kitchen ranges, etc., an& 
attach it directly to hoods placed over such apparatus.. 



'276 ELECTRICAL TABLES AND DATA 

In wide or square rooms provide several ventilators so 
as to secure a more uniform movement of air over the 
whole space. If fan capacity is small compared to 
size of room and cooling is the only consideration it is 
best to blow air into the room. An exhaust fan which 
does not change the air oftener than it is naturally 
changing has little effect. Even in well constructed 
places the air is supposed to change itself once per I 
hour at least. 

Voltage Regrdation. — In a network of wiring the 
regulation is always fairly good because a heavy de- 
mand at any point immediately causes current from 
all sides to rush in. The drop at feeder ends can be 
easily compensated for if they are all of the same 
length. If they are not of the same length they should 
be divided into groups of the same length and each 
group separately regulated. For d. c. work individual 
feeder regulators waste too much energy to be con- 
sidered except with very short lines. 

In long lines a booster is often installed. To deter- 
mine whether it is profitable to install a booster we 
must compare its cost and the losses due to its opera- 
tion, with the cost of increasing the size of conductors 
proportionately and the losses incident to the im- 
proved lines. Obviously this depends upon the length 
of the line, and the drop which may be allowed. De- 
termine investment for booster, interest and deprecia- 
tion and cost of operation and losses. This amount 
can be saved by the installation of proper feeders, 
and if we can obtain the larger feeders by an invest- 
ment of capital upon which the above sum will be the 
proper interest it will not be profitable to install the 
booster. 

For a. c. work individual feeder regulators are much 
used, and as they waste comparatively little energy, 
they may be used in each feeder and all feeders con- 
nected to a common line. Such regulators may be 



ELECTRICAL TABLES AND DATA 27? 

arranged either to boost or choke. For low tension 
work, either a. c. or d. c, pressure wires are often run 
from the end of feeder back to switchboard to indicate 
the pressure at feeder end. The same object is also 
attainable by line drop compensators, or if the size and 
length of line be known the drop at the far end or 
any other point may be calculated from the number 
of amperes. 

The^ following table (LXXXXVI) is provided to 
assist in making the necessary calculations for the set- 
ting of a. c. line drop compensators, and also to deter- 
mine the drop in voltage occurring at any part of the 
line so that the voltage at the station may be raised 
correspondingly. 

To find the drop in voltage we may use the formula 
IZxd; in which / is the current in amperes; Z the 
impedance as given in the table for various sizes of 
wire and separation, and d the number of 1,000 feet 
of line. 

For line compensators it is necessary to find the 
percentage of the reactive, and ohmic drop. The same 
formula may be used substituting X or R for Z and 
dividing the result by the transmission voltage. This 
will give the percentage according to which the two 
sections of the compensator must be set. See detail 
instructions sent out with compensators. The values 
of Z, R and X are for 1,000 feet of wire. A single 
phase installation can be served by a single compen- 
sator, but then the drop will be double that given, or 
for 2,000 feet instead of 1,000 feet of wire. The same 
may be said of a two phase installation which is served 
by two compensators, but in two phase three wire, or 
in three phase systems, a compensator must be in- 
stalled in each wire, and a four wire three phase sys- 
tem requires four, so that in connection with these 
systems the value given in the table need not be 
doubled. 



ELECTRICAL TABLES AND DATA 



TABLE LXXXXVI 



Table Showing Resistance, Eeactance and Impedance of 1,000 
Feet of Wire of Sizes Given and at Various Separations. 



B. & S. 


R 


12 
X Z 


Separation of Wires in Inches. 
24 36 48 60 

x z xzxz xz 


X 


z 


8 


.627 


.126 


.640 


.142 


.640 


.151 


.640 


.157 


.640 


.163 


.640 


.167 


.640 


6 


.397 


.120 


.415 


.136 


.415 


.145 


.420 


.152 


.420 


.157 


.420 


.161 


.420 


5 


.314 


.118 


.345 


.134 


.350 


.143 


.355 


.150 


.357 


.155 


.360 


.159 


.362 


4 


.250 


.115 


.275 


.131 


.2S0 


.140 


.285 


.147 


.290 


.152 


.292 


.156 


.294 


3 


.198 


.112 


.230 


.128 


.235 


.137 


.240 


.144 


.245 


.150 


.248 


.153 


.251 


z 


.157 


.110 


.190 


.126 


.200 


.135 


.205 


.141 


.212 


.147 


.215 


.151 


.217 


1 


.126 


.107 


.165 


.123 


.175 


.132 


.180 


.139 


.187 


.144 


.191 


.148 


.194 





.100 


.104 


.145 


.120 


.155 


.129 


.165 


.136 


.169 


.141 


.173 


.145 


.176 


00 


.079 


.102 


.130 


.118 


.140 


.127 


.150 


.133 


.156 


.139 


.159 


.143 


.162 


000 


.063 


.099 


.120 


.115 


.130 


.124 


.140 


.131 


.145 


.136 


.149 


.140 


.153 


0000 


.050 


.096 


.110 


.112 


.125 


.122 


.135 


.128 


.138 


.133 


.140 


.137 


.146 



Weights of Materials in Pounds (Approximate). — 
Aluminum, cu. ft., 167 ; cu. in., 0.095. For wires, see 

tables. 
Antimony, cu. ft., 418; cu. in., 0.242. 
Asphaltum, cu. ft, 84; gal., 11.2. 

Bismuth, cu. ft., 612; cu. in., 0.354. 
Brass, cu. ft, 522 ; cu. in., 0.302. 
Brick, cu. ft., 119 ; per thousand, 4500. 
Bronze, cu. ft, 537; cu. in., 0.311. 

Cement, loose, cu. ft, 88 ; bu., 95. 

Charcoal; cu. ft., 25 ; bu., 27. 

Coal, anthracite, piled loose, cu. ft., 52 ; bu., 56. 

" bituminous, piled loose, cu. ft., 50; bu., 54. 
Coke, piled loose, cu. ft., 27 ; bu., 29. 



ELECTRICAL TABLES AND DATA 279 

Concrete, eu. ft., 150 ; cu. yd., 4050. 

Copper, cu. ft, 555; cu. in., 0.321. For wires, see 

tables. 
Cork, cu. ft., 15.6. 
Crushed Stone, cu. yd., 2700. 

Earth, cu. ft., 109; cu. yd., 2943. 

Glass, cu. ft., 165. 

Gold, cu. ft, 1225 ; cu. in., 0.709. 

Gravel, cu. ft., 119 ; cu. yd., 3213. 

Ice, cu. ft, 56; cu. yd., 1512. 

Iridium, cu. ft., 1400; cu. in., 0.81. 

Iron, cu. ft., 490 ; cu. in., 0.225. For wires, see tables. 

Lead, cu. ft., 709; cu. in., 0.41. 

Limestone, cu. ft., 165 ; cu. yd., loose, 2700. 

Loam, cu. ft, 78; cu. yd., 2106. 

Mercury, cu. ft, 850; cu. in., 0.492. 

Nickel, cu. ft., 540; cu. in., 0.312. 

Oils, olive, gal., 7.6. 

" cottonseed, gal., 8.0. 

11 linseed, gal., 7.8. 

" turpentine, gal., 7.2. 

" lard, gal., 7.9. 

" whale, gal., 7.8. 

" gasoline, gal., 5.7. 

" petroleum, gal., 7.3. 

" mineral lubricating, gal., 7.8. 

Paper, cu. ft., 56. 

Paraffine, cu. ft., 56 ; gal., 7.41. 

Pitch, cu. ft., 67 ; gal., 8.9. 



2S0 ELECTRICAL TABLES AND DATA 

Platinum, cu, ft., 1340 ; eu. in., 0.718. 
Porcelain, cu. ft., 150; en. in., 0.087. 

Salt, cu. ft., 60; gal., 8.04. 
Sand, cu. ft., 105; cu. yd., 2835. 
Silver, cu. ft., 653 ; cu. in., 0.377. 
Slate, cu. ft., 184; cu. in., 0.109. 
Sulphur, cu. ft., 125. 

Tantalum, cu, ft., 1040; cu. in., 0.60. 
Tar, cu. ft., 62.5 ; gal., 8.33. 
Tin, cu. ft., 455; cu. in., 0.263. 
Tungsten, cu. ft, 1175; cu. in., 0.68. 



Water, plain, cu. ft., 


62.5; 


gal., 8.33. 


sea, cu. ft., 79 


; gal., 


10.3. 


Wood, ash, cu. : 


it, 46 


per 1000 ft., 3850. 


' ' butternut, ' 


1 28 


2330. 


1 ' cedar, 


1 38 


3165. 


' ' chestnut, 


1 39 


3250. 


1 1 cypress, 


1 35 


2915. 


' ' elm, 


1 36 


3000. 


"fir, 


1 35 


2915. 


1 ' hemlock, 


1 27 


2250. 


1 ' hickory, 


' 55 


4600. 


1 ' lignum vitae, ' 


' 81 


6750. 


1 ' mahogany ' 


1 36 


3000. 


1 ' maple, 


1 50 


4560. 


' ' oak, 


1 47 


3915. 


" pine, white, ' 


1 25 


2275. 


11 pine, yellow, l 


1 45 


3750. 


1 1 poplar, 


4 24 


2200. 


1 ' redwood, 


1 30 


2740. 


1 ' spruce, 


1 28 


2330. 


' ' walnut, 


4 41 


3400. 



Zinc, cu. ft., 420; cu. in., 0.243. 



ELECTRICAL TABLES AND DATA 281 

Contents of Barrels or Round Containers = average 
diameter squared x height x 0.7854. 
If measurements are taken in inches 

D 2 xHx 0.000454 = cu. ft. 
D 2 xHx 0.0034 =gal. 
D 2 x H x 0.000425 = bu. 

If cubic contents are known in feet, multiply by 
7.58 to obtain gallons, and by 0.936 to obtain bushels. 
To obtain cubic yards divide by 27. 

Welding. — From 30 to 60 H. P. per square inch 
area of weld to be made are used. This is the power 
required to be delivered to welder. The greater the 
capacity the shorter will be the time required to make 
a weld. In some cases only a few seconds are required. 

Wire Calculations. — This division contains the 
following tables: 

A table of carrying capacities of copper and alumi- 
num wires. 

A table showing carrying capacities of different 
combinations of wires. 

Table for determining the total wattage of groups 
of lamps or other devices usually rated in watts. 

Tables for calculating the amperage per H. P. of 
motors at various efficiencies and power factors. 

Tables showing maximum H. P. allowed on wires 
according to N. E. C. rules and carrying capacities. 

Tables for determining proper size of wire for a 
certain loss in voltage; copper and aluminum wires, 
direct current, and 60 and 25 cycles. 

Tables to facilitate determining the most economical 
conductors. 

Various tables showing physical properties of cop- 
per, aluminum, copper clad, german silver and steel 
wires. 

Tables showing outside diameters of wires and 
cables. 



282 



ELECTRICAL TABLES AND DATA 



TABLE LXXXXVIII 
Table of Allowable Carrying Capacity of Wires. 



^B. & S. 


Bubber Insulation 


Other 


[nsulations 


'Gauge 


Copper 


Aluminum 


Copper 


Aluminum 


18 


3 


2 


5 


4 


16 


6 


5 


10 


8 


14 


15 


12 


20 


17 


12 


20 


17 


25 


21 


.10 


25 


21 


30 


25 


8 


35 


29 


50 


42 


6 


50 


42 


70 


59 


5 


55 


46 


80 


67 


4 


70 


59 


90 


76 


3 


80 


67 


100 


84 


2 


90 


76 


125 


105 


1 


100 


84 


150 


126 





125 


105 


200 


168 


00 


150 


126 


225 


189 


000 


175 


147 • 


275 


231 


0000 


225 


189 


325 


273 


^Circular 










Mils 










200000 


200 


168 


300 


252 


300000 


275 


231 


400 


336 


400000 


325 


273 


500 


420 


500000 


400 


336 


600 


504 


600000 


450 


378 


680 


571 


700000 


500 


420 


760 


639 


800000 


550 


462 


840 


705 


900000 


600 


504 


920 


773 


1000000 


650 


546 


1000 


840 


1100000 


690 


580 


1080 


901 


1200000 


730 


613 


1150 


966 


1300000 


770 


646 


1220 


1024 


1400000 


810 


680 


1290 


1083 


1500000 


850 


714 


1360 


1142 


1600000 


890 


748 


1430 


1201 


1700000 


930 


781 


1490 


1251 


1800000 


970 


815 


1550 


1301 


1900000 


1010 


848 


1610 


1352 


.2000000 


1050 


882 


1670 


1402 



ELECTRICAL TABLES AND DATA 283 

Carrying Capacities of Different Combinations of 
Wires. — Owing to the relatively different radiating 
surface of wires of different sizes the carrying capacity 
per circular mil is not the same for all wires, and 
where wires of different gauge number are to be con- 
nected in parallel this must be taken into account. In 
the following table this is done and the carrying ca- 
pacity of smaller wires at the current density allowed 
for the larger wires is given wherever the horizontal 
and vertical lines pertaining to any two wires cross. 
The number found at this place indicates the am- 
perage the smaller wire will have with the larger wire 
fully loaded. The figures are based on the carrying 
capacities given by the National Electrical Code. To 
find the proper wire to reinforce another which has 
been overloaded: Select the horizontal line pertain- 
ing to the larger wire and follow along this line until 
a number about equal to the necessary additional 
amperes is found. At the head of the vertical column 
in which this number is found will be found the gauge 
number of the proper wire to be used. 



ELECTRICAL TABLES AND DATA 



TABLE LXXXXIX 

Table Showing Combined Carrying Capacity of Different 
Wires — Eubber Insulation 



Amps. B.&S. 
15 14 



20 

25 

35 

50 

55 

70 

80 

90 

100 

125 

150 

175 

225 



5 
4 
3 

2 

1 



00 

000 

0000 



14*12 10 
15 

12 20 
10 15 25 
8 13 22 



8 6 5 4 3 2 



00 000 0000 



275 300000 
325 400000 
400 500000 



12 20 

11 17 

11 18 

10 16 

9 14 

8 12 

7 12 

7 11 

6 10 

7 11 
6 9 



35 
31 50 

27 44 55 

28 45 55 70 

25 39 50 64 80 
22 35 45 56 71 90 
19 31 39 49 63 80 
19 31 39 49 62 77 
18 30 37 47 59 74 
17 27 34 43 54 69 
17 28 35 44 56 76 
15 24 30 38 48 61 
13 21 26 33 43 54 
13 21 26 33 42 53 

Other Insulations 



100 
98 125 
94 118 150 
87 108 138 175 
89 112 141 178 225 
77 96 122 154 194 
68 85 109 137 172 
67 84 106 134 169 



Amps. B&S. 14 
20 14 20 



12 10 8 6 5 4 3 2 1 00 000 0000 



25 

30 

50 

70 

80 

90 

100 

125 

150 

200 

225 

275 

325 



12 15 
10 11 
8 12 
6 10 
5 10 
4 10 
3 7 



2 
1 


00 

000 

0000 



400 300000 
500 400000 
600 500000 



25 

19 30 
19 31 
17 27 
16 25 
16 25 
12 19 
12 19 

11 18 

12 19 
11 17 
10 17 
10 16 

8 14 
8 13 
8 12 



50 

44 70 
40 64 
40 64 
31 50 
31 50 
29 47 
31 49 
28 44 
27 43 
25 40 
22 35 
20 33 
20 31 



80 
80 90 
63 80 
63 78 
59 74 
62 79 
56 70 
54 68 
51 64 
44 55 
41 52 
40 50 



100 
99 125 
94 118 150 
99 125 157 200 
89 112 141178 225 
86 109 137 173 218 275 
81 102 128 162 204 258 325 
70 88 112 140 177 223 282 
66 83 104 132 166 209 264 
63 80100127160 202 255 



ELECTRICAL TABLES AND DATA 285 

TABLE C 

Table for determining total wattage required for 
incandescent lamps or other devices usually rated in 
watts. 

To find total wattage add all numbers found where 
lines pertaining to number of lamps and wattage of 
same cross. 



Number 


















of 






Watts 












lamps 1000 


750 


500 


250 


150 


100 


m 


40 


25 


2 


2000 


1500 


1000 


500 


300 


200 


120 


80 


50 


3 


3000 


2250 


1500 


750 


450 


300 


180 


120 


75 


4 


4000 


3000 


2000 


1000 


600 


400 


240 


160 


100 


5 


5000 


3750 


2500 


1250 


750 


500 


300 


200 


125 


6 


6000 


4500 


3000 


1500 


900 


600 


360 


240 


150 


7 


7000 


5250 


3500 


1750 


1050 


700 


420 


280 


175 


8 


8000 


6000 


4000 


2000 


1200 


800 


480 


320 


200 


9 


9000 


6750 


4500 


2250 


2700 


900 


540 


360 


225 


10 


10000 


7500 


5000 


2500 


1500 


1000 


600 


400 


250 


15 


15000 


11250 


7500 


3750 


2250 


1500 


900 


600 


375 


20 


20000 


15000 


10000 


5000 


3000 


2000 


1200 


800 


500 


25 


25000 


18750 


12500 


6250 


3750 


2500 


1500 


1000 


625 


30 


30000 


22500 


15000 


7500 


4500 


3000 


1800 


1200 


750 


35 


35000 


26250 


17500 


8750 


5250 


3500 


2100 


1400 


875 


40 


40000 


30000 


20000 


10000 


6000 


4000 


2400 


1600 


1000 


45 


45000 


33750 


22500 


11250 


6750 


4500 


2700 


1800 


1125 


50 


50000 


37500 


25000 


12500 


7500 


5000 


3000 


2000 


1250 


55 


55000 


41250 


27500 


13750 


8250 


5500 


3300 


2200 


1375 


60 


60000 


45000 


30000 


15000 


9000 


6000 


3600 


2400 


1500 


65 


65000 


48750 


32500 


16250 


9750 


6500 


3900 


2600 


1625 


70 


70000 


52500 


35000 


17500 


10500 


7000 


4200 


2800 


1750 


75 


75000 


56250 


37500 


18750 


11250 


7500 


4500 


3000 


1875 


80 


80000 


60000 


40000 


20000 


12000 


8000 4800 


3200 


2000 


85 


85000 


63750 


42500 


21250 


12750 


8500 


5100 


3400 


2125 


90 


90000 


67500 


45000 


22500 


13500 


9000 


5400 


3600 


2025 


100 


100000 


75000 


50000 


25000 


15000 


10000 


6000 


4000 


2500 


110 


110000 


82500 


55000 


27500 


16500 


11000 


6600 


4400 


2750 


120 


120000 


90000 


60000 


30000 


18000 


12000 


7200 


4800 


3000 


130 


130000 


92500 


65000 


32500 


19500 


13000 


7800 


5200 


3250 


140 


140000 


105000 


70000 


35000 


21000 


14000 


8400 


5600 


3500 


150 


150000 


112500 


75000 


37500 


22500 


15000 


9000 


6000 


3750 



ELECTRICAL TABLES AND DATA 









TABLE CI 






Table showing wattage capacity of different 


wires. 




—110 Volts— 


—220 Volts— 


—440 Volts— 




Eubber 


Other 


Eubber 


Other 


Eubber 


Other 




Ins. 


Ins. 


Ins. 


Ins. 


Ins. 


Ins. 


14 


1650 


2200 


3300 


4400 


6600 


8800 


12 


2200 


2750 


4400 


5500 


8800 


11000 


10 


2750 


3300 


5500 


6600 


11000 


13200 


8 


3850 


5500 


7700 


11000 


15400 


22000 


6 


5500 


7700 


11000 


15400 


22000 


30800 


5 


6050 


8800 


12100 


17600 


24200 


35200 


4 


7700 


9900 


15400 


19800 


30800 


39600 


3 


8800 


11000 


17600 


22000 


35200 


44000 


2 


9900 


13750 


19800 


27500 


39600 


55000 


1 


11000 


16500 


22000 


33000 


44000 


66000 





13750 


22000 


27500 


44000 


55000 


88000 


00 


16500 


24750 


33000 


49500 


66000 


99000 


000 


19250 


30250 


38500 


60500 


77000 


121000 


0000 


24750 


35750 


49500 


71500 


99000 


143000 


200000 


22000 


33000 


44000 


66000 


88000 


132000 


300000 


30250 


44000 


60500 


88000 


121000 


176000 


400000 


35750 


55000 


71500 


110000 


143000 


220000 


500000 


44000 


66000 


88000 


132000 


176000 


264000 



If system is balanced use columns 220 volts for 
3-wire 110-volt systems and column 440 volts for 
3-wire 220 volt systems or for such voltages direct. 

Tables for calculating amperage of motors with 
various efficiencies, power factors systems and voltages. 

RULE FOR FINDING AMPERES 

In top part of table select numbers found where 
lines pertaining to efficiency and power factors cross 
and find same number in middle table. In same line 
under proper system will be found the number of 
amperes required for 1 H. P. at 110 volts. In bottom 
table select divisor pertaining to higher voltages, di- 
vide amperes by this and multiply by number of H. P. 
The result will give the total number of amperes re- 
quired. The efficiency of small motors is always much 
less than that of larger motors. 



ELECTRICAL TABLES AND DATA 









TABLE CII 








to 






Efficiency 








O c8 

PMfa 


.95 .90 


.87£ 


.85 .82* 


.80 .75 


.70 


.65 .60 


.55 


.95 


.90 .86 


.83 


.81 .78 


.76 .71 


.67 


.62 .57 


.53 


.90 


.86 .81 


.79 


.77 .74 


.72 .68 


.63 


.59 .54 


.50 


.85 


.81 .77 


.74 


.72 .70 


.68 .64 


.60 


.55 .51 


.47 


.80 


.76 .72 


.70 


.68 M 


.64 .60 


.56 


.52 .48 


.44 


.75 


.71 .68 


.66 


.64 .62 


.60 .56 


.53 


.49 .45 


.41 


.70 


.67 .63 


.61 


.59 .58 


.56 .53 


.49 


.46 .42 


.39 




Amperes for 1 H. 


P. at 110 Volts 






Direct 






Direct 








current 


Two 


Three 


current 


Two Three 




or s. phase phase 


phase 


or s. phase 


phase phase 


.39 


17.4 


12.5 


10.0 


.66 


10.3 


7.3 


5.9 


.41 


16.5 


11.9 


9.6 


.67 


10.1 


7.2 


5.9 


.42 


16.1 


11.6 


9.3 


.68 


9.9 


7.1 


5.8 


.44 


15.4 


11.1 


8.9 


.70 


9.7 


7.0 


5.6 


.45 


15.1 


10.8 


8.7 


.71 


9.6 


6.9 


5.5 


.46 


14.7 


10.5 


8.6 


.72 


9.5 


6.8 


5.4 


.47 


14.4 


10.3 


8.4 


.74 


9.2 


6.6 


5.3 


.48 


14.1 


10.2 


8.2 


.76 


8.9 


6.4 


5.1 


.49 


13.8 


9.9 


8.0 


.77 


8.8 


6.3 


5.1 


.50 


13.6 


9.7 


7.8 


.78 


8.7 


6.2 


5.0 


.51 


13.3 


9.5 


7.6 


.79 


8.6 


6.1 


5.0 


.52 


13.0 


9.4 


7.5 


.81 


8.4 


6.0 


4.8 


.53 


12.8 


9.2 


7.4 


.83 


8.2 


5.9 


4.7 


.54 


12.6 


9.0 


7.3 


.84 


8.1 


5.8 


4.6 


.55 


12.4 


8.8 


7.1 


.85 


8.0 


5.7 


4.6 


.56 


12.1 


8.7 


7.0 


.86 


7.9 


5.7 


4.5 


.57 


11.9 


8.5 


6.8 


.90 


7.5 


5.4 


4.3 


.58 


11.7 


8.4 


6.7 


.92 


7.4 


5.3 


4.3 


.59 


11.5 


8.3 


6.6 


.93 


7.3 


5.2 


4.2 


.60 


11.3 


8.1 


6.5 


.94 


7.2 


5.2 


4.2 


.61 


11.1 


8.0 


6.4 


.95 


7.1 


5.1 


4.1 


.62 


10.9 


7.8 


6.3 


.96 


7.0 


5.1 


4.1 


.63 


10.7 


7.7 


6.2 


.97 


7.0 


5.0 


4.0 


.64 


10.6 


7.6 


6.1 


.98 


6.9 


4.9 


4.0 








Voltages 










110 


220 


440 550 650 


1100 


2080 


2200 


Divisor 1 


2 


4 5 


5.9 


11 


18.9 


20 



ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 






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294 ELECTRICAL TABLES AND DATA 

Tables for Calculating Drop in Voltage. — The drop 
in voltage in a direct current circuit is always equal to 
IR, while in an alternating current circuit it is equal 
to IZ. These formulae are, however, not well suited 
for use when the problem is to find the proper wire to 
be used where the loss is determined upon. 

That portion of the following tables devoted to 
direct currents consists simply of one column of fig- 
ures in which are given the conductances of the vari- 
ous wires. That part of the tables used for alternating 
current circuits gives the admittances of the various 
wires under different circumstances. The losses in 
voltage which form the basis of the following tables 
have been calculated from the formula : 

^[(Exp.f.) + (IB)] 2 + [(Exr.f.) + (IX) ] 2 = l 

where E stands for voltage to be delivered at end of 
line; p.f. for power factor of load; I for current in 
amperes; R for ohmic resistance of line; r.f. for re- 
active factor ; X for reactive volts in line, and E 1 for 
the e. m. f . necessary at the starting point to deliver E 
at the end of line. The ohmic resistance and the react- 
ive volts can be taken from Tables CIX and CX and 
the power factor (cosine of angle of lag) and reactive 
factor (sine of angle of lag) from Table CXI. To 
obtain the loss in volts it is necessary to subtract E 
from E 1 . Eeferring to Figure 34, which illustrates 
the common method of figuring drop in voltage for 
alternating current circuits, the losses for which the 
tables are calculated are equal to the difference be- 
tween the lines A and B. 

Having thus briefly outlined how the line losses, 
used as the basis of the following tables have been 
derived, we may now proceed to explain the tables and 
the method of their use. 



ELECTRICAL TABLES AND DATA 295 

Since, according to a transposition of Ohms law, 

-pi j ^ i i 

— =B it follows that -^ = u- In other words -w or ~ 
i Mi K K /j 

give us the conductance or admittance which in con- 
nection with the current 1 will consume the voltage E. 
The numerical value of conductance or admittance in 
any line equals the number of amperes which can be 
.transmitted over that line at a loss of one volt. This 
conductance for direct currents and admittance for 
alternating currents has been tabulated in the follow- 
ing pages. Hence, if we divide the current to be trans- 




Figure 34. 



mitted by the volts we wish to lose we shall obtain 
the value of the conductance or admittance which is 
necessary to cause this loss. The basis of the table is 
a line of 100 feet in length, which represents 200 feet 
of wire of a two-wire line. In order to find a wire 
which shall give us any desired loss, we need then 
merely to find what that loss is to be per 100 feet of 
line, and divide the amperes to be transmitted by this 1 
loss; then trace down the column describing the con- 
ditions (direct current or separation of wires) until 
we come to a number which about equals the one 
previously found. In connection with three-phase 
systems, if great accuracy is required, it will be neces- 
sary to divide the volts to be lost by 0.86 before pro- 
ceeding with the rest. 



296 ELECTRICAL TABLES AND DATA 

In order to facilitate the calculations, the tables, 
CXII to CXIII, have been added. Table CXII gives 
the average value of amperes per H. P. with various 
voltages, and table CXIII shows the value in actual 
volts per hundred feet run of 1 per cent loss with the 
distances and voltages given. If the loss to be allowed 
over any distance and with any of the voltages given 
is stated in per cent, we need merely to multiply the 
number found where distance and voltage cross by 
the number of per cent to find the number of volts 
to be lost per 100 feet. 

Example: We have 50 H. P., three-phase, 60 
cycles, at 1000 volts, to transmit a distance of 2200 
feet, with 24-inch separation, at a loss of 5 per cent. 
What size of wire must be used? Fifty H.P. three 
phase at 1000 volts equals 35 amperes. (See Table 
CXII.) For a voltage of 1000 and a distance of 2200 
feet the number with which we must divide our cur- 
rent for one per cent is .451. (See Table CXIII.) 

This multiplied by the percentage of loss, 5 = 2.255, 
and this, in turn, divided by 0.86, gives us 2.62, with 
which we divide our amperes, 35, and obtain 13.3 as 
the admittance required. Tracing downward in table 
CXIV under the proper separation, 24 inches, we 
find the number 14.2 as the nearest, and this indicates 
a No. 5 wire. The same plan is used for direct cur- 
rent, and the conductances are given in column D. C. 
If larger wires are indicated, the conductances of the 
larger wire are in proportion to the circular mils for 
direct current. 



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TABLE CXI 



Power and Eeactive Factors for Different Angles of Lag or 
Lead 



o3 


l-e 


©02 

> 00 


o3 


l-e 


©02 


ci 


l-e 


©02 
> 03 




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© a 
£*5 


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2 © 


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03 © 


2 s- 


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2 u 


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© oj 


i? ^H 


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© oj 


P o 


PhQ 


tfft 


P O 


PhO , 


Mfe 


P o 


PhQ 


Mfr 


1 


.999 


.017 


31 


.857 


.515 


61 


.485 


.875 


2 


.999 


.035 


32 


.848 


.530 


62 


.469 


.883 


3 


.998 


.052 


33 


.839 


.545 


63 


.454 


.891 


4 


.997 


.070 


34 


.829 


.559 


64 


.438 


.899 


5 


.996 


.087 


35 


.819 


.574 


65 


.423 


.906 


6 


.994 


.105 


36 


.809 


.588 


66 


.407 


.914 


7 


.992 


.122 


37 


.798 


.602 


67 


.391 


.921 


8 


.990 


.139 


38 


.788 


.616 


68 


.375 


.927 


9 


.988 


.156 


39 


.777 


.629 


69 


.358 


.934 


10 


.985 


.174 


40 


.766 


.643 


70 


.342 


.940 


11 


.982 


.191 


41 


.755 


.656 


71 


.326 


.946 


12 


.978 


.208 


42 


.743 


.669 


72 


.309 


.951 


13 


.974 


.225 


43 


.731 


.682 


73 


.292 


.956 


14 


.970 


.242 


44 


.719 


.695 


74 


.276 


.961 


15 


.966 


.259 


45 


.707 


.707 


75 


.259 


.966 


16 


.961 


.276 


46 


.695 


.719 


76 


.242 


.970 


17 


.956 


.292 


47 


.682 


.731 


77 


.225 


.974 


18 


.951 


.309 


48 


.669 


.743 


78 


.208 


.978 


19 


.946 


.326 


49 


.656 


.755 


79 


.191 


.982 


20 


.940 


.342 


50 


.643 


.767 


80 


.174 


.985 


21 


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.358 


51 


.629 


.777 


81 


.156 


.988 


22 


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.375 


52 


.616 


.788 


82 


.139 


.990 


23 


.920 


.391 


53 


.602 


.799 


83 


.122 


.992 


24 


.914 


,407 


54 


.588 


.809 


84 


.105 


.994 


25 


.906 


.423 


55 


.574 


.819 


85 


.087 


.996 


26 


.899 


.438 


56 


.560 


.829 


86 


.070 


.997 


27 


.891 


.454 


57 


.545 


.839 


87 


.052 


.998 


28 


.883 


.470 


58 


.530 


.848 


88 


.035 


.999 


29- 


.875 


.485 


59 


.515 


.857 


89 


.017 


.999 


30 


.866 


.500 


60 


.500 


,866 









SOO ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 30£ 

Economy of Conductors. — Any system of electrical 
conductors may be designed with reference to any of 
the following conditions: 

1. The conductors may be designed for minimum 
first cost, regardless of waste or quality of service. 

2. The conductors may be designed for the best 
possible service regardless of cost. 

3. The conductors may be designed for a minimum 
cost of generating plant. 

4. The conductors- may be designed for maximum 
general economy of operation and installation; i. e. t 
to yield the most profitable results in the long run. 

5. The conductors may be designed for a minimum 
first cost of generating plant and conductors. 

The first problem is solved by selecting the smallest 
wire allowed, either by heating limitations, or mechan- 
ical considerations. 

The second problem is solved by selecting very large 
wires, thus reducing the loss to any desired minimum. 

The third condition is fulfilled by selecting such 
large wires that the generator will not be called upon 
to deliver much waste power. 

The fourth problem has heretofore required some 
very extensive and elaborate calculations, but with the 
tables following, these have been reduced to a 
minimum and can be made in a few moments. This 
is, moreover, a subject which has been very much 
neglected, especially in connection with short runs 
such as are used inside of buildings, or to connect one 
building with another. The general practice has been 
to figure on a loss of from 2 to 5 per cent, or to dis- 
regard all question of economy and work from the 
standpoint of minimum first cost entirely. 

It must be understood that a certain loss in elec- 
trical transmission is unavoidable, and that the nearer 
we approach to an efficiency of 100 per cent the more 
copper proportionately will be required to reduce the 



306 ELECTRICAL TABLES AND DATA 

remaining loss. For instance, if we have a certain 
wire causing a loss of 10 per cent, by adding another 
wire just like it we reduce our loss to 5 per cent; by 
adding two more similar wires we reduce the loss only 
2J per cent more, and by adding four more wires of 
the same size we gain only 1J per cent more. In 
other words, the original wire was capable of trans- 
mitting 90 per cent of our energy; two wires 95 per 
cent, four wires 97J per cent, and eight wires 98} per 
cent. That under such circumstances it is easy to 
spend more in trying to save the energy than it is 
worth, is evident. It has been shown by Sir Wm. 
Thompson and others that the most economical loss is 
that at which the annual value of the energy lost 
equals the interest charge on the cost of line construc- 
tion necessary to save it. In making calculations on 
this subject we need have nothing to do with the total 
length of line, or even the total cost of the line; we 
need be concerned only with the difference in cost 
between installing any convenient length of the small- 
est wire permissible, and that of substituting a larger 
wire. In some cases this may cause no other expense 
except that of the larger wire, in other cases it may be 
necessary to reconstruct the whole line in order to 
make room for larger wires. 

The basis of the following tables is found in the 
proposition and formula below : 



R 



-) xl 2 xpxh- 



\1000xc 1000 x 

the maximum capital which may economically be 
invested to substitute a larger wire in place of the 
smallest permissible wire where: 

R equals the resistance of the smallest wire con- 
sidered, 

r the resistance of the larger wire to be considered, 



ELECTRICAL TABLES AND DATA 307 

c the interest rate applicable (governed by the num- 
ber of years line is to remain in use), 

/ the current to be transmitted, 

p the rate per K. W. and 

h the number of hours / is used per year. 

In connection with this formula we need not con- 
sider the whole length of line, but may take any con- 
venient portion of it ; therefore, in these tables a run 
of 100 feet (200 feet of wire) is taken as the basis of 
all calculations. 

The rate of interest applicable in this formula is 
the following : If line is to be in use only one year it 
must pay a dividend of 106 per cent ; two years, 56 ; 
three years, 40; four years, 32; five years, 27; six 
years, 24 ; seven years, 21J ; eight years, about 20, and 
nine years, 18f per year. 

In table CXVIII the values have been calculated for 
all of the wire sizes given, 1 2 can be easily calculated 
and p and h can be found, for many values thereof, 
in table CXIX. The figures in table CXVIII have all 
been carried out to seven decimal points in order to 
simplify the comparison of small wires with the larger 
ones, and also to obtain greater accuracy. In most 
<cases, however, when comparing small wires, it will 
not be necessary to use the full figures, and one or 
more figures at the right may be dropped. 

In using the tables it will be best to first find the 
quantity (I 2 xpxh), as this is fixed in any given 
problem. Next determine the smallest wire permis- 
sible, either on account of safety rules, mechanical 
considerations, or perhaps because it is already in- 
stalled. Note the number given in horizontal line in 
which the B&S gauge number is found and under 
the column pertaining to the number of years line is 
to remain in service ; from this number subtract the 
corresponding number pertaining to some larger wire 
and with the remainder multiply the quantity Ipk 



S08 ELECTRICAL TABLES AND DATA 

previously determined. This will give us the sum in 
dollars which may economically be invested to substi- 
tute the larger wire in place of the smaller. Bear in 
mind that this is only for a length of run of 100 feet. 
Example : We wish to find whether it will be profit- 
able to substitute a No. 6 wire in place of a No. 14 
carrying a load of 15 amperes, the rate per K. W. 
being 3 cents, the current to be used 1000 hours per 
year, and the line assumed to remain in use five 
years, at the end of which time it will be worthless. 
Three cents times 1000 hours gives us $30.00; 
this multiplied by 225 (I 2 ) gives us 6750. We now 
subtract .0002944 (No. 6) from .0018229 (No. 14), 
which leaves us (omitting the last three decimals) 
.0016; multiplying 6750 by this, we have 10.8, which 
is the number of dollars we may spend to install a 
No. 6 instead of a No. 14 wire. The difference in 
cost between a No. 14 and a No. 6 is from about ten 
to twelve dollars, not figuring the cost of supports. 

The foregoing calculations are assumed to be made 
from the standpoint of an engineer who connects onto 
an established system and who is responsible only for 
the actual loss in watts occurring on his part of the 
line. Sometimes, however, a line must be laid out 
from the central station, and the point then is not 
only the wattage loss, but also the loss in generator 
capacity. In this connection the length of the line 
is the principal consideration, and it becomes a ques- 
tion whether it is cheaper to provide a certain excess 
capacity in the generator and allow this to be lost 
in a small transmission line, or to provide a heavier 
line and use the generator pressure more economically. 
In lines of this character boosters are usually resorted 
to to regulate the pressure. 

The standard central station system usually soon 
evolves into an interconnected system of wires in 
which no accurate calculations on loss can be made. 



ELECTRICAL TABLES AND DATA 309 

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TABLE CXX 

Copper Wire Table 

Bureau of Standards, Washington, D. C. 

Working Table, International Standard Annealed Copper 
American Wire Gauge (B. & S.) 



Diam 

Gauge in 

No. Mils 


. , Cross 

Circular 
Mils 


Section * 

Square 
Inches 


/—Ohms per 
25° C 
(=77° F) 


1000 Feet-^ 

65° C 

(=149° F) 


Pounds 
per 
1000 Feet 


0000 


460. 


212 000. 


0.166 


0.0500 


0.0577 


641. 


000 


410. 


168 000. 


.132 


.0630 


.0727 


508. 


00 


365. 


133 000. 


.105 


.0795 


.0917 


403. 





325. 


106 000. 


.0829 


.100 


.116 


319. 


1 


289. 


83 700. 


.0657 


.126 


.146 


253. 


2 


258. 


66 400. 


.0521 


.159 


.184 


201. 


3 


229. 


52 600. 


.0413 


.201 


.232 


159. 


4 


204. 


41 700. 


.0328 


.253 


.292 


126. 


5 


182. 


33 100. 


.0260 


.319 


.369 


100. 


6 


162. 


26 300. 


.0206 


.403 


.465 


79.5 


7 


144. 


20 800. 


.0164 


.508 


.586 


63.0 


8 


128. 


16 500. 


.0130 


.641 


.739 


50.0 


9 


114. 


13 100. 


.0103 


.808 


.932 


39.6 


10 


102. 


10 400. 


.008 15 


1.02 


1.18 


31.4 


11 


91. 


8230. 


.006 47 


1.28 


1.48 


24.9 


12 


81. 


6530. 


.005 13 


1.62 


1.87 


19.8 


13 


72. 


5180. 


.004 07 


2.04 


2.36 


15.7 


14 


64. 


4110. 


.003 23 


2.58 


2.97 


12.4 


15 


57. 


3260. 


.002 56 


3.25 


3.75 


9.86 


16 


51. 


2580. 


.002 03 


4.09 


4.73 


7.82 


17 


45. 


2050. 


.001 61 


5.16 


5.96 


6.20 


18 


40. 


1620. 


.001 28 


6.51 


7.51 


4.92 


19 


36. 


1290. 


.00101 


8.21 


9.48 


3.90 


20 


32. 


1020. 


.000 802 


10.4 


11.9 


3.09 


21 


28.5 


810. 


.000 636 


13.1 


15.1 


2.45 



ELECTRICAL TABLES AND DATA 



TABLE CXX— Continued 





Diam. 


, Cross 


Section , 


r- Ohms per 


1000 Feet-^ 


Pounds 


luge 


in 


Circular 


Square 


25° C 


65° C 


per 


«Io. 


Mils 


Mils 


Inches 


(=77° F) 


(=149° F) 


1000 Feet 


22 


25.3 


642. 


.000 505 


16.5 


19.0 


1.94 


23 


22.6 


509. 


.000 400 


20.S 


24.0 


1.54 


24 


20.1 


404. 


.000 317 


26.2 


30.2 


1.22 


25 


17.9 


320. 


.000 252 


33.0 


38.1 


0.970 


26 


15.9 


254. 


.000 200 


41.6 


48.0 


.769 


27 


14.2 


202. 


.000 158 


52.5 


. 60.6 


.610 


28 


12.6 


160. 


.000 126 


66.2 


76.4 


.484 


29 


11.3 


127. 


.000 099 5 


83.4 


96.3 


.384 


30 


10.0 


101. 


.000 078 9 


105. 


121. 


.304 


31 


8.9 


79.7 


.000 062 6 


133. 


153. 


.241 


32 


8.0 


63.2 


.000 049 6 


167. 


193. 


.191 


33 


7.1 


50.1 


.000 039 4 


211. 


243. 


.152 


34 


6.3 


39.8 


.000 031 2 


266*. 


307. 


.120 


35 


5.6 


31.5 


.000 024 8 


335. 


387. 


.0954 


36 


5.0 


25.0 


.000 019 6 


423. 


488. 


.0757 


37 


4.5 


19.8 


.000 015 6 


533. 


616. 


.0600 


38 


4.0 


15.7 


.000 012 3 


673. 


776. 


.0476 


39 


3.5 


12.5 


.000 009 8 


848. 


979. 


.0377 


40 


3.1 


9.9 


.000 007 8 


1070. 


1230. 


.0299 



Note. 1. — The table is based on the international standard 
of resistance for copper, which takes the fundamental mass 
resistivity = 0.15328 ohm (meter, gram) at 20° C, the corre- 
sponding temperature coefficient = 0.00393 at 20° C, and the 
density = 8.89 grams per cc at 20° C. The temperature 
coefficient is proportional to the conductivity, whence the 
change of mass resistivity per degree C is a constant, 
0.000597 ohm (meter, gram). 

Note 2. — The values given in the table are only for an- 
nealed copper of the standard resistivity. The user of the 
table must apply the proper correction for copper of any 
other resistivity. Hard-drawn copper may be taken as about 
2.7 per cent higher resistivity than annealed copper. 

Note 3. — Ohms per mile, or pounds per mile, may be ob- 
tained by multiplying the respective values above by 5.28. 

Note 4. — For complete tables and other data see Circular 
No. 31 of the Bureau of Standards. 

Bureau of Standards, Washington, D. C, 1914 



ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 



TABLE CXXII 

Aluminum Company of America 

Stranded Aluminum Wire 

Diameter and Properties 

Conductivity at 62 in the Matthiessen Standard Scale 



Number 

B. & S. Circular 

Gauge Mils. 


DIAMETERS WEIGHT IN POUNDS 

Triple Braid Resistance 

Decimal Nearest BARE Insulated in Ohms. 

Parts 32nd Per Per at 70° F 

of an of an 1000 Per 1000 per 

Inch. Inch. Feet. Mile. Feet. 1000 Ft 




. 1000000 


1.152 


1A 


920. 


4858. 


1406. 


.016726 




950000 


1.125 


li 


874. 


\ 4617. 


1337. 


.017606 




900000 


1.092 


1A 


828. 


4374. 


1268. 


.018585 




850000 


1.062 


ift 


782. 


4131. 


1199. 


.019679 




800000 


1.035 


1A 


736. 


3888. 


1129. 


.020907 




750000 


.996 


l 


690. 


3645. 


1060. 


.022301 




700000 


963 


U 


644. 


3402. 


990. 


.023894 




650000 


.928 


IS 


598. 


3159. 


921. 


.025734 




600000 


.891 


M 


552. 


2916. 


852. 


.027878 




550000 


.854 


11 


506. 


2673. 


782. 


.030411 




500000 


.814 


\l 


460. 


2430. 


713. 


.033450 




450000 


.772 


M 


414. 


2187. 


644. 


.037170 




400000 


.725 


If 


368. 


1944. 


575. 


.041818 




350000 


.679 


tt 


322. 


1701. 


506. 


.047789 




300000 


.621 


f 


276. 


1458. 


436. 


.055755 




250000 


.567 


A 


230. 


12.15 


366. 


.066905 


000( 


) 211600 


.522 


U 


195. 


1028. 


313. 


.079045 


00( 


) 167805 


.464 


U 


155. 


816. 


253. 


.099675 


oc 


133079 


.414 


II 


123. 


647. 


204. 


.12569 


( 


) 105534 


.368 


i 


97. 


513. 


165. 


.15849 


] 


I 83694 


.328 


u 


77. 


407. 


135. 


.19984 


i 


5 66373 


.291 


A 


61. 


323. 


112. 


.25200 


I 


I 52634 


.261 


i 


48.5 


256. 


93.5 


.31779 


4 


[ 41742 


.231 


& 


38.5 


203. 


76.5 


.40069 


i 


> 33102 


.206 


3i 


30.2 


161. 


56.0 


.50530 


( 


5 26250 


.180 


& 


24.1 


128. 


47.0 


.63720 



ELECTRICAL TABLES AND DATA 



TABLE CXXIII 
Aluminum Company of America 

Weight of Aluminum, Wrought Iron, Steel, Copper and Brass 
Wire. 

Diameters determined by American (Brown & Sharpe) Gauge. 

Water at 62° Fahrenheit, 62.355 lbs. per cubic foot. 



Drawn Wrought 
Steel 
" Copper 
" Brass 


Iron is 2.8724 times heavier than Drawn Aluminum. 
" 2.9322 " 
" 3.3321 " 
" 3.1900 " 


No. Size of 
of each 
Gauge No. 
Inch 


Weight of Wire per 
Ft. per lb. 
Alumi- Alumi- Wro't 
num num Iron Steel 
Feet Lbs. Lbs. Lbs. 


L000 Lineal Feet 

Copper Brass 
Lbs. Lbs. 


3000 


.46000 


. 5.185 


192.86 


553.97 565.50 


642.68 


615.21 


000 


.40964 


6.539 


152.94 


439.33 


448.45 


509.32 


487.92 


00 


.36480 


8.246 


121.28 


348.40 


355.65 


404.20 


386.94 





.32486 


10.396 


96.18 


276.30 


282.02 


320.50 


306.83 


1 


.28930 


13.108 


76.29 


219.11 


223.68 


254.20 


243.35 


2 


.25763 


16.529 


60.50 


173.78 


177.38 


201.60 


192.98: 


3 


.22942 


20.846 


47.97 


137.80 


140.67 


159.86 


153.02 


4 


.20431 


26.281 


38.05 


109.28 


111.57 


126.78 


121.37 


5 


.18194 


33.146 


30.17 


86.68 


88.46 


100.54 


96.26 


6 


.16202 


41.789 


23.93 


68.73 


70.15 


79.72 


76.32 


7 


.14428 


52.687 


18.98 


54.43 


55.56 


63.23 


60.53- 


8 


.12849 


66.445 


15.05 


43.23 


44.12 


50.14 


48.00 


9 


.11443 


83.822 


11.93 


34.28 


34.99 


39.77 


38.07 


10 


.10189 


105.68 


9.462 27.18 


27.74 


31.53 


30.181 


11 


.090742 


133.24 


7.505 21.56 


22.01 


25.01 


23.94 


12 


.080808 


168.01 


5.952 17.10 


17.46 


19.83 


18.99 


13 


.071961 


211.86 


4,720 13.56 


13.84 


15.73 


15.06 


14 


.064084 


267.17 


3.74 


3 10.75 


10.98 


12.47 


11.94 



318 



ELECTRICAL TABLES AND DATA 



Size of 
No. each 
of No. 
Gauge Inch 


Ft. per lb. 
Alumi- 
num 
Feet 


r-Weight of Wire per 1000 Lineal Feet-^ 

Alumi- Wro't 
num Iron Steel Copper Brass 
Lbs. Lbs. Lbs. Lbs. LbSi. 


15 


.057068 


336.93 


2.968 


8.526 


8.704 


9.890 


9.468 


16 


.050820 


424.81 


2.354 


6.761 


6.903 


7.843 


7.508 


17 


.045257 


535.62 


1.867 


5.362 


5.474 


6.220 


5.955 


18 


.040303 


675.67 


1.480 


4.252 


4.342 


4.933 


4.723 


19 


.035890 


851.79 


1.174 


3.372 


3.443 


3.912 


3.755 


20 


.031961 


1074.11 


.9310 


2.672 


2.730 


3.102 


2.970 


21 


.028462 


1356. 


.7382 


2.121 


2.165 


2.460 


2.355 


22 


.025347 


1707.94 


.5855 


1.682 


1.717 


1.951 


1.868 


23 


.022571 


2153.78 


.4643 


1.333 


1.361 


.547 


1.481 


24 


.020100 


2715.91 


.3682 


1.058 


1.080 


1.227 


1.175 


25 


.017900 


3424.66 


.2920 


.8388 


.8563 


.9731 


.9316 


26 


.015940 


4317.78 


.2316 


.6652 


.6791 


.7716 


.7387 


27 


.014195 


5446.63 


.1836 


.5276 


.5385 


.6120 


.5858 


28 


.012641 


6868.13 


.1456 


.4183 


.4270 


.4853 


.4645 


29 


.011257 


8657.5 


.1155 


.3317 


.3386 


.3849 


.3683 


30 


.010025 


10917.0 


.0916 


.2631 


.2686 


.3052 


.2922 


31 


.008928 


13762.8 


.0727 


.2087 


.2130 


.2421 


.2318 


32 


.007950 


17361.1 


.0576 


.1655 


.1693 


.1919 


.1837 


33 


.007080 


21886.7 


.0457 


.1312 


.1340 


.1522 


.1457 


34 


.006304 


27622. 


.0362 


.1040 


.1062 


.1207 


.1155 


35 


.005614 


34807.3 


.0287 


.0825 


.0842 


.0957 


.0916^ 


36 


.005000 


43878.9 


.0228 


.0655 


.0668 


.0759 


.0727 


37 


.004453 


55245. 


.0181 


.0519 


.0530 


.0602 


.0577 


38 


.003965 


69783.7 


.0143 


.0413 


.0420 


.0478 


.0457 


39 


.003531 


88028.2 


.0114 


.0326 


.0333 


.0379 


.0363 


40 


.003144 110980. 


.0090 


.0259 


.0264 


.0300 


.0287 



Specific gravity Wire... 2.680 7.698 7.858 8.930 8.549 
Wt., per cu. ft., Wire. . 167.111 480.000 490.000 556.830 533.073 



ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 



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ELECTRICAL TABLES AND DATA 323 



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ELECTRICAL TABLES AND DATA 

TABLE CXXVII 
18% German Silver Resistance Wire. 

"Weight 









Resistance 


Lbs. 




No. 






per 


per 




B. &S. 


Diam. 


Area 


1000 Ft. 


1000 Ft. 


Ohms 


Gauge 


Ins. 


C. M. 


at 75° F. 


Bare 


PerLU 





.325 


105,625 


1.95 


302 


.00645 


1 


.289 


83,521 


2.53 


239 


.01025 


2 


.258 


66,564 


3.22 


190 


.0163 


3 


.229 


52,441 


4.14 


150 


.0259 


4 


.204 


41,616 


5.18 


119 


.0412 


5 


.182 


33,124 


6.55 


95 


.0656 


6 


.162 


26,244 


8.28 


72 


.1042 


7 


.144 


20,736 


10.47 


59 


.1657 


8 


.128 


16,384 


13.22 


47 


.2635 


9 


.114 


12,996 


16.68 


37.6 


.4189 


10 


.102 


10,404 


20.8 


29.2 


.6663 


11 


.091 


8,281 


26.2 


23.7 


1.059 


12 


.081 


6,561 


33.2 


18.8 


1.684 


13 


.072 


5,184 


42 


14.8 


2.619 


14 


.064 


4,096 


53 


11.7 


4,258 


15 


.057 


3,249 


67 


9.3 


6.773 


16 


.051 


2,601 


84 


7.45 


10.768 


17 


.045 


2,025 


107 


5.73 


17.121 


18 


.040 


1,600 


136 


4.57 


27.216 


19 


.036 


1,296 


168 


3.7 


43.281 


20 


.032 


1,024 


222 


2.93 


68.838 


21 


.0285 


812.3 


270 


2.32 


109.45 


22 


.0253 


640.1 


340 


1.83 ' 


174.03 


23 


.0226 


510.8 


425 


1.46 


276.78 


24 


.0201 


404.0 


540 


1.15 


439.95 


25 


.0179 


320.4 


680 


.91 


699.72 


26 


.0159 


252.8 


864 


.72 


1,112.4 


27 


.0142 


201.6 


1,076 


.58 


1,768.8 


28 


.0126 


158.8 


1,370 


.46 


2,811.9 


29 


.0113 


127.7 


1,700 


.365 


4,473 


30 


.010 


100.0 


2,180 


.286 


7,011 


31 


.0089 


79.2 


2,750 


.266 


11,306 


32 


.008 


64.0 


3,400 


.183 


17,980 


33 


.0071 


50.4 


4,300 


.144 


28,581 


34 


.0063 


39.7 


5,480 


.113 


45,465 


35 


.0056 


31.4 


6,920 


.090 


72,261 


36 


.005 


25.0 


8,700 


.071 


114,933 


37 


.0045 


20.2 


11,000 


.058 


182,742 


38 


.004 


16.0 


13,850 


.046 


291,270 


39 


.0035 


12.2 


17,550 


.035 


462,000 


40 


.003 


9.0 


22,200 


.026 


887,250 



ELECTRICAL TABLES AND DATA 325 

The composition commonly known as German Silver is 
that containing 18% of nickel. Its resistance varies some- 
what in different lots, and according to temper, and is 
approximately 21 times that of copper. 

30% German Silver Wire has a resistance approximately 
28 times that of copper. 



TABLE CXXVIII 

Properties of Galvanized Telephone and Telegraph Wires. 

Based on Standard Specifications. 

American Steel and Wire Co. 



d 

53 M 


11 

5.2 


<- h Approximate 

5| wt. in lbs. 

rt g bj Per Approximate 

Eisg iOOO Per breaking 

<Jo§ feet mil© strain in lbs. 


Res. per mile 
(Latent Ohms) 
at 68° F.. 20° C. 








Ex. 

B.B. B.B. Steel 


Ex. 
B.B. 


B.B. 


Steel 





340 


115600 


313 1655 4138 4634 4965 


2.84 


3.38 


3.93 


1 


300 


90000 


244 1289 3223 3609 3867 


3.65 


4.34 


5.04 


2 


284 


80656 


218 1155 2888 3234 3465 


4.07 


4.85 


5.63 


3 


259 


67081 


182 960 2400 2688 2880 


4.90 


5.83 


6.77 


4 


238 


56644 


153 811 2028 2271 2433 


5.80 


6.91 


8.01 


5 


220 


48400 


131 693 1732 1940,2079 


6.78 


8.08 


9.38 


6 


203 


41209 


112 590 1475 1652 1770 


7.97 


9.49 


11.02 



7 180 32400 87 463 1158 1296 1389 10.15 12.10 14.04 

8 165 27225 74 390 975 1092 1170 12.05 14.36 16.71 

9 148 21904 60 314 785 879 942 14.97 17.84 20.70 

10 134 17956 49 258 645 722 774 18.22 21.71 25.29 

11 120 14400 39 206 515 577 618 22.82 27.19 31.55 

12 109 11881 32 170 425 476 510 27.65 32.94 38.23 

13 95 9025 25 129 310 347 372 37.90 45.16 52.41 

14 83 6889 19 99 247 277 297 47.48 56.56 65.66 

15 72 5184 14 74 185 207 222 63.52 75.68 87.84 

16 65 1*225 11 61 152 171 183 77.05 91.80 106.55 



326 



ELECTRICAL TABLES AND DATA 



TABLE CXXIX 

Approximate Outside Dimensions of Wires and Cables 

The table below is for the use of those who wish to esti- 
mate carrying capacities of conductors without cutting into 
insulation or shutting down a plant. The figures given are 
thought to be an average for voltage up to 600. Weather- 
proof dimensions are for minimum thickness allowed by 
N. E. C. 



Rubber Covered 



Weatherproof Lead Covered 



53 

2000000 
1750000 
1500000 
1250000 
1000000 
950000 
900000 
850000 
800000 
750000 
700000 
650000 
600000 
550000 
500000 
450000 
400000 
350000 
300000 
250000 
225000 



a 

3 
2% 

2y 32 

17s 

1% 

1 3 %4 
l 3l /64 

1 2 %4 
1 2 %4 
1 2 %4 
1 2 %4 
1 2 % 



So a> 5u <o So 

S<S £S ft S£ 



n% 

l 12 /64 

!%4 

1%4 

1%4 

6 %4 

6 %4 

57 /64 

5 /%4 



64% 4 7200 
625/ 64 6300 
55% 4 5550 
5S% 4 4700 
45% 4 3900 
446/ 64 3750 
43% 4 3575 
43% 4 3400 
42% 4 3250 
4i7/ 64 3000 
4% 4 2850 
4i/ 64 2835 
35% 4 2575 
34% 4 2325 
334/ 64 2130 
325/ 64 1925 
3i% 4 1735 
36/ 64 1525 
25% 4 1360 
25i/ 64 1185 
245/ 64 975 



156/ 64 557/ 64 

14% 4 5 35/ 64 

1*%4 513/ 64 

13% 4 4C%4 

126/ 64 427/ 64 



P^ 
.o 

•4J o 

£s 

7008 
6190 
5375 
4500 
3675 



120/ 64 4% 4 3330 

ll% 4 35% 4 3000 
liy M 35% 4 2800 
l 12 /64 347/ 64 2650 

l7/ 64 335/ 64 2250 

1%4 325/ 64 1900 

6i/ 64 263/ 64 1700 

5 %4 25% 4 1550 

56/ 64 248/ 64 1350 

52/ 64 235/ 64 1175 

4 %4 228/ 64 985 



3 o a> . O 

ft 0<H R r-l 



z%4 0^/ 6 4 
2 2 /64 625/ 64 
l60/ 64 6%4 
150/ 64 538/ 64 
13% 4 54/ G4 
135/ 64 455/ 64 
133/ 64 449/ 64 
133/ 64 446/ 64 
13%4 44% 4 
128/ 64 433/ 64 
126/ 64 428/ 64 
124/ 64 420/ 64 
1 2 %4 41% 4 
1 2 %4 414/ 64 
11% 4 350 /6 4 
H2/64 347/ 64 
H%4 341/64 
1% 4 325/64 
1%4 312/ 64 
61 /64 3 



11300 
10225 
9100 
7950 
6280 
6050 
5800 
5580 
5350 
5110 
4880 
4640 
4385 
4150 
3480 
3225 
3000 
2750 
2480 
2230 



ELECTRICAL. TABLES AND DATA 327 



TABLE CXXX 



Approximate Outside Diameter of Wires and Cables 
Bubber Covered, to 600 Volts 











Wt. per 




B. &S 


. Solid- ~ 


-Stranded- 


1000 


Duplex 




S.B. 


D.B. 


S.B. 


D.B. 


feet 


Solid 


-Stranded- 


0000 


4 %4 


47 /64 


4 %4 


52/ 64 


850 


4 %4 X 9^ 


5 %4 X 9% 4 


000 


4 %4 


4 %4 


4 %4 


4 %4 


700 


44 /64 X 8% 4 


4 %4 X 92/ 64 


00 


3 %4 


4 %4 


41 /64 


44 /64 


575 


41 /64 X 77/ 64 


4 %4 X 83/ 64 





3 %4 


3 %4 


3%4 


41 /64 


475 


3 %4 X 71/ 64 


41 /64 X 78/ 64 


1 


32 /64 


3 %4 


3 %4 


3 %4 


375 


3 %4 X 66/ 64 


3 %4 X 7% 4 


2 


2 %4 


31 /64 


3 %4 


3 %4 


300 


31/ 64 X 58/ 64 


3 %4 X 6% 4 


3 


2 %4 


2 %4 


2 %4 


3l /64 


260 


2 %4 X 54/ 64 


31 /64 X 58/ 64 


4 


24 /64 


27 /64 


2 %4 


2 %4 


215 


2 %4 X 51/ 64 


3 %4 X 54/ 64 


5 


23/ 64 


2 %4 


2 %4 


27 /64 


185 


2 %4 X 48/ 64 


27 /64 X 5% 4 


6 


21 /64 


2 %4 


23 /64 


2 %4 


150 


2 %4 X 45/ 64 


2 %4 X 48^ 


8 


17 /64 


2 %4 


18 /64 


21 /64 


100 


21 /64 X 31/ 64 


22 /64 X 3% 4 


10 


15 /64 


18 /64 


16 /64 


19 /64 


75 


19 /64 X 3% 4 


2 %4 X 35/ 64 


12 


14 / 6 4 


17 /64 


!%4 


18 /64 


60 


17 /64 X 31/ 64 


18 /64 X 32/ 64 


14 


13 /64 


16 /64 


14 /64 


17 /64 


45 


16 /64 X 28/ 64 


17 /64 X ?%4 


16 


10 /64 


13 /64 






30 


13 /64 X 2% 4 





18 % 4 i% 4 20 l% 4 X 2i/ 64 

600 to 3500 Volts 

0000 46/ 64 4 %4 51/ 64 54/ 64 850 50/^ X 94/ 64 54/ 64 X 10% 4 

000 43/ 64 46/ 64 47/ 64 50/ 64 700 %X% 5 %4 X 9% 4 

00 3 %4 4 %4 43/ 64 46/ 64 575 43/ 64 X 81/ 64 46/ 64 X 8% 4 

37/ 64 40/ 64 40/ 64 43/ 64 475 %X% %X% 

1 34 /64 37 /64 37 /64 4 %4 375 3 %4 X 7 %4 40/ 64 X 7 %4 

2 3 %4 35/ 64 300 36/ 64X 66/ 64 37/^ X 71/ 64 

3 30/ 64 33/ 64 34/ 64 37/ 64 260 «*%4 X «%4 3 %4 X % 

4 28/ 64 31/ 64 30/ 64 33/ 64 215 32/ 64> <59/ 64 3%^ X «%4 

5 27/ 64 30/ 64 32/ 64 35/ 64 185 % X 5%4 32/ 64 X 5% 4 

6 26/ 64 29/ 64 27/ 64 30/ 64 150 2 %4 X 54/ 64 30/ 64 X 56/ 64 
8 23 /k 26/ 64 24/ 64 . 27/ 64 100 27/ 64 < X 4% 4 28/ 64 X 52/ 64 

10 2 %4 25/ 64 22/ 64 24/ 64 7 5 2 %4 X 4% 4 2^ X 4%^ 

12 20/ 64 23/ 64 21/ 64 24/ 64 60 24/ 64X 43/ 64 2$fe X 4fo 

14 1%4 2 %4 2 %4 2 %4 45 23/ 64 X41/ 64 23/ 64 X 41/ 64 

Weights given are thought to be average weights; duplex 

wires weigh nearly double the amounts given. 



ELECTRICAL TABLES AND DATA 



TABLE CXXXI 

Approximate Weight and Diameters of Rubber Covered Lead 
Encased Cables 

Single Conductor to 600 Volts Duplex Conductor 

Wt. per Wt. per 

B. &S. Diameter 1000 ft. Diameter 1000 ft. 

0000 5% 4 1600 5% 4 x H%4 2900 

000 5i^ 4 1400 5% 4 x 9% 4 2600 

00 49/ 64 1250 47/ 64 x 9% 4 2300 

45/ 64 1100 44/ 64 X 78/ 64 2000 

1 38/ 64 900 39/ 64 X 68/ 64 1700 

2 34/ 64 750 38/ 64 x 6% 4 1400 
4 29/ fi4 500 3% 4 x 56/ 64 1100 
6 26/ fi4 400 28/ 64 x so/ 64 800 
8 22/ fi4 300 2 %4 x 4 %4 600 

10 2i/ 64 275 2i/ 64 x 3% 4 500 

12 i% 4 175 i% 4 X sy 64 350 

14 l%4 150 %X 3% 4 300 



ELECTRICAL TABLES AND DATA 
TABLE CXXXII 



329 



8ths. 


leths. 


32nds. 


64ths. 


Mils. 


8ths. 


16ths. 


32nds. 


64ths. 


Mils. 








1 

2 
3 

4 

5 
6 

7 
8 

9 
10 
11 
12 

.. 13 


15.6 
31.2 
46.9 
62.5 

78.1 
93.7 
109.3 

125. 

140.6 

156.2 
171.8 
187.5 

203.1 
218.7 
234.3 
250. 

265.6 
281.2 
296.8 
312.5 

328.1 
343.7 
359.3 
375. 

390.6 
406.2 
421.8 
437.5 

453.1 

468.7 
484.3 
500. 








33 
34 
35 
36 

37 
38 
39 
40 

41 
42 
43 
44 

45 
46 
47 
48 

49 
50 
51 
52 

53 
54 
55 
56 

57 
58 
59 
60 

61 
62 
63 
64 


515.6 






1 






17 


531.2 










546.8 




l 


2 




9 


18 


562.5 
578.1 






3 






19 


593 7 










609.3 


1 


2 


4 


5 


10 


20 


625. 
640.6 






5 






21 


656.2 










671.8 




3 


6 




11 


22 


687.5 
703.1 






7 


14 
15 
16 

17 
18 
19 
20 

21 
22 
23 
24 

25 

26 
27 
28 

29 
30 
31 
32 






23 


718.7 










734.3 


2 


4 


8 


6 


12 


24 


750. 
765.5 






9 






25 


781.2 










796.8 




5 






13 


26 


812.5 
828.1 






..11.. 






27 


843.7 








859.3 


3 


6 


12 


7 


14 


28 


875. 
890 6 






..13.. 






29 


906.2 








921 8 




7 






15 


30 


937.5 
953.1 






..15.. 






31 


968.7 








9S4.3 


4 


8 


16 


8 


16 


32 


1000. 



CARRYING CAPACITIES OF WIRES FOR SHORT PERI- 
ODS AND INTERMITTENT LOADS. 

The following tables of carrying capacities were 
prepared by the use of formulae deduced by the 
authors from heating curves of a large number of 
conductors experimentally determined in the labora- 
tories of the Commonwealth Edison Co. of Chicago. 
The tests were made at the suggestion of the Depart- 
ment of Gas and Electricity of the City of Chicago 
and in some of these tests the engineers of the above 
company were assisted by engineers of the city de- 
partment. A full description of these tests was given 
in the Electrical "World during 191$. 

The data used in compiling the figures given were 
obtainable only in the form of "curves." It is well 
known that such curves are to a large extent an inter- 
polation of values, and it is therefore quite unlikely 
that many of the values given would produce exactly 
the temperature assigned to them if subject to a test. 
A study of the curves showed that in a general way 
the temperature rise in any given conductor was pro- 
portional to the square of the current used, but there 
were also some exceptions, due probably to errors of 
observation and interpolation as well as to a variety 
of causes. 

In order to eliminate these errors as much as pos- 
sible, and at the same time provide a simple means of 

330 



ELECTRICAL. TABLES AND DATA 331 

interpolation to determine the carrying capacity of 
such wires as were not tested, the amperage necessary 
to bring each size of wire to a certain temperature was 
first computed. After this had been done, the circu- 
lar mils of the conductor were divided by the amper- 
age found, thus giving the circular mils per ampere. 

The circular mils per ampere of all the conductors 
tested were then plotted vertically, while the copper 
contents were laid out horizontally, and the whole 
combined in the form of a curve in the well known 
way. The. final carrying capacity was then deter- 
mined by dividing the circular mils in the conductor 
by the circular mils per ampere indicated by the 
curve. It is believed that, in this manner, fairly ac- 
curate average values have been obtained. 

The current which will cause a given temperature 
rise in a conductor can be found by the following; 
formula : 

I=xi JT~ 

in which T is the desired temperature ; t the tempera- 
ture attained in the conductor by the current i and 
I is the current to be found. This formula does not 
take into account the fact that the resistance of the 
conductor increases with the temperature, as this is 
considered negligible for all practical purposes. The 
values of t and i are given in the tables for rubber 
covered wires. Those conductors, in connection with 
which no temperature rises are given, were not tested,. 
but the current values given were obtained by interpo- 
lation as before explained. 

The tables applying to conduits also give the di- 
mensions of the conduits used in the tests. Under 
the heading, "N. E. Code," we give the amperage 



332 ELECTRICAL TABLES AND DATA 

allowed by the code. Under the heading, ' ' Calculated 
Carrying Capacities," we give those calculated as 
described above. These values must not be used in 
conflict with the official figures given by the code, as 
they are not yet sanctioned) thereby. The amper- 
ages given under, ' ' Short Time in Minutes, ' ' are those 
which it is believed the various conductors can safely 
carry for the length of time given, provided no appre- 
ciable heating has been caused before this load is ap- 
plied. 

Four tables are given. Two of them are calculated 
for a temperature rise of 72 degrees Fahrenheit, and 
the other for 36 degrees Fahrenheit. They are also 
arranged for open and concealed wires, the latter in 
conduit. The three wires run in conduit were all 
carrying the same current and the heating effect there 
obtained will be exceeded only in cases where the 
four wires of a two-phase system are run in the same 
pipe. With the ordinary three-wire lighting system, 
the heating will be considerably less. 

The temperature of rubber covered wire should not 
exceed 120 degrees F. but that covered with other 
insulations may rise to 150 degrees, and asbestos cov- 
ered wires may be carried to higher temperatures 
than this. 

The following tables are intended to assist in the 
selection of the smallest conductor that may be used 
to carry an intermittent load. The ultimate tempera- 
ture rise of a conductor subject to an intermittent 
load depends upon the ratio between the "on" and 
"off" time of the current. Unless the current is off 
long enough to allow the loss of the heat accumulated 
-during the "on" time, the temperature will rise. 

At low temperatures the dissipation of heat pro- 



ELECTRICAL TABLES AND DATA 333 

ceeds slowly, but at higher temperatures it is much 
more rapid. For this reason, the relative time in 
which a given quantity of heat can be dissipated 
varies greatly with the temperature permitted. 

A separate table is provided for each size of wire 
considered; in conduit as well as for open wiring. 
Each table is divided into two parts. In the left hand 
portion of the tables is given the time in seconds re- 
quired for the currents given at the top, under the 
heading, "Heating Load; Amperes," to raise the tem- 
perature of the wire 5 degrees F. within the range of 
temperature given under the heading, "Temperature 
Range," in conduit or open wires as the case may be. 

Thus, referring to the table for No. 14 wire in con- 
duit, we see that a current of 25 amperes will produce 
a rise of 5 degrees, between the range of 47 and 52, 
in 220 seconds, but also that it will require 1,350 
seconds to effect a temperature rise from 67 to 72 in 
the same conductor by the same 1 current. In this 
connection we need not pay any attention to the lower 
temperatures, as we are interested only as the critical 
temperatures are approached. 

If an intermittent load is continued long enough, 
there will be a steady rise in temperature until the 
point is reached at which the dissipation of heat equals 
the supply. Therefore, if we allow sufficient cooling 
time, we can keep the temperature within bounds. 

In the right hand portion of the tables we give the 
time in seconds required to dissipate the heat gen- 
erated during the time given in the same horizontal 
lines. 

Thus, again referring to the table for No. 14 wire, 
we see that with a temperature range of 22-27 degrees, 
the heat produced in 110 seconds requires 300 seconds 



334 ELECTRICAL TABLES AND DATA 

to cool off, while if we allow the temperature to go to 
57-62, that generated in 400 seconds will be lost in 
40 seconds. Cooling times are given with zero load 
as well as with continued loads of the amperages 
given. 

The temperature of rubber covered wire should not 
be allowed to rise above 120 degrees Fahrenheit, and 
that of ' ' Other Insulations ' ' should not go above 150 
degrees F. Asbestos covered wires, however, may be 
allowed to run much hotter. In order to facilitate the 
selection of the proper conductor there is provided 
a column "Limiting Outer Temperature." A sepa- 
rate column is provided for rubber covered and other 
insulation covered wires. The figures there given in- 
dicate that, in locations where the temperature of the 
air does not rise above the values given, the tempera- 
ture of the conductor may be allowed to rise to the 
value of the highest figure given in the same horizontal 
line under the heading "Temperature Range,' ' either 
in conduit or open wires. 

The simplest method of using the tables consists of 
first determining the limiting outer temperature. 
Next find the peak number of amperes and the length 
of time in seconds during which this amperage is 
used. Then proceed to find the minimum amperage 
and the length of time during which it is in use. 
Make notes of these values and always estimate them 
with a view to obtaining the hardest operating condi- 
tions likely to occur. Now proceed to find the small- 
est wire under which the amperage in question is given 
and, selecting the horizontal line in which the limiting 
temperature is found, see whether the ratio of the on 
and off times corresponding to the temperature given 
is the same as that in the problem. 



ELECTRICAL, TABLES AND DATA 335 

Example: "We have a peak load of 80 amperes 
which lasts for 60 seconds and is then reduced to 25 
amperes for 200 seconds ; this being the estimated 
regular cycle of operation of the circuit. Wires are in 
conduit. The smallest wire under which an amperage 
of 80 or more is found is a No. 8. Here we find, in 
the horizontal line pertaining to 83 degrees P., that 
105 amperes will cause a temperature rise of 5 degrees 
in 21 seconds and that this heat, even with only ITV^ 
amperes in continued use, requires 285 seconds for 
its dissipation. This will not do, and we proceed to 
the next size of wire. Here we find, in the correspond- 
ing horizonal line, that 80 amperes will require 100 
seconds to raise the temperature of the wire 5 degrees, 
and that this heat will be lost in 300 seconds, even with 
25 amperes in continued use. Furthermore, as the 
cooling time is three times as long in this case, while 
in our problem it was three and one-third times as 
long, the wire thus found will not heat quite as much 
as indicated and will therefore be safe to use. 



336 



ELECTRICAL, TABLES AND DATA 



Table CXXXII 
Wires in Conduit 
Table of Carrying Capacities; three conductors in conduit, 
each carrying same current. 
20° C; 36° F. temperature rise above surrounding air. 
Use this table for rubber covered wires in conduit where 
temperature of air does not exceed 85° F., and for other 
insulations at temperatures from 85° F. to 125° F. 





Size 


N. E. 


CODE 


Calculated Carrying Capacities 36° 


F. rise 


B. & S. 




$** 


la 1 


sajrmtin ui 


eon} Jaoqs 


gauge. 


:onduit 




S-cl 


|*1 


30 


15 


10 


5 


14 


y 2 " 


15 


27.0 


17 


19 


22 


24 


30 


12 


%" 


20 


31.0 


22 


24 


26 


29 


35 


10 


%" 


25 


27.9 


27 


30 


35 


40 


45 


8 


i " 


35 


29.9 


36 


43 


50 


60 


65 


6 


i " 


50 


33.1 


52 


60 


73 


80 


105 


5 




55 




56 


69 


88 


100 


125 


4 


ivi" 


70 


4*0.7 


64 


77 


97 


110 


140 


3 


1V4" 


80 


34.9 


82 


93 


113 


135 


165 


2 


iy 2 " 


90 


34.7 


90 


106 


130 


155 


195 


1 


iy 2 " 


100 


39.1 


96 


126 


154 


180 


225 





2 " 


125 


41.2 


110 


147 


182 


210 


275 


2/0 


2 " 


150 


41.8 


130 


179 


220 


260 


340 


3/0 


2 " 


175 


39.4 


150 


213 


270 


320 


420 


200000 




200 




175 


247 


310 


355 


480 


4/0 


2y 2 ; ' 


225 


57.6 


180 


256 


325 


395 


515 


250000 




240 




205 


297 


375 


455 


585 


300000 


3* ' " 


275 


45.2 


238 


345 


435 


535 


690 


350000 




300 




265 


395 


500 


605 


790 


400000 


%'"" 


325 


4*2*1 


290 


440 


555 


690 


850 


500000 


3 " 


400 


48.1 


345 


529 


660 


800 


1090 


600000 




450 




390 


610 


750 


915 


1225 


700000 




500 




430 


680 


830 


1025 


1400 


750000 


4 "'' 


525 


44.8 


450 


710 


870 


1080 


1450 


800000 




550 




465 


745 


905 


1120 


1525 


900000 




600 




495 


810 


975 


1210 


1665 


1000000 


4V 2 ' ; 


650 


55.2 


525 


870 


1040 


1295 


1800 



ELECTRICAL. TABLES AND DATA 



337 



Table CXXXIII 
Wires in Conduit 
Table of Carrying Capacities; three conductors in conduit, 
each carrying same current. 
40° C; 72° F. temperature rise above surrounding air. 
Use this table for "Other insulations" in conduit where 
temperature does not exceed 80° F., and for rubber covered 
wire where temperature of air does not exceed 50° F. 





Size 


N. E. 


CODE 


Calculated Carrying Capacities 72° 


F. rise 


B. &S. 


« 




^ to 










gauge. 


conduit 






'3 °? £ 

is a 


Short time 


in minutes 




30 


15 


10 


5 


14 


w 


15 


27.0 


24 


26 


31 


34 


42 


12 


%" 


20 


31.0 


30 


33 


37 


41 


50 


10 


%" 


25 


27.9 


38 


43 


50 


55 


65 


8 


1 " 


35 


29.9 


50 


60 


70 


85 


95 


6 


1 " 


50 


33.1 


70 


86 


105 


115 


150 


5 




55 




80 


95 


125 


140 , 


isa 


4 


ivi" 


70 


40*7 


90 


110 


140 


155 


200 


3 


VA." 


80 


34.9 


110 


130 


150 


190 


235 


2 


iy 2 " 


90 


34.7 


125 


150 


175 


220 


275 


1 


1%" 


100 


39.1 


135 


175 


215 


250 


31& 





2 " 


125 


41.2 


140 


205 


255 


290 


385 


2/0 


2 " 


150 


41.8 


185 


245 


310 


360 


440 


3/0 


2 " 


175 


39.4 


215 


300 


380 


430 


565 


200000 




200 




240 


350 


430 


520 


675 


4/0 


2W f 


225 


57.6 


250 


360 


455 


550 


720 


250000 




240 




280 


420 


525 


640 


820 


300000 


3 '" 


275 


45.2 


335 


485 


610 


750 


965 


350000 




300 




375 


560 


700 


845 


1105 


40000C 


z"» 


325 


42.1 


415 


630 


775 


965 


1190 


500000 


3 " 


400 


48.1 


480 


750 


925 


1130 


1520 


600000 




450 




545 


860 


1050 


1280 


1700 


700000 




500 




600 


950 


1160 


1435 


1960 


750000 


4"// 


525 


44.8 


630 


1020 


1220 


1510 


2030 


800000 




550 




660 


1050 


1260 


1560 


2135 


900000 




600 




700 


1140 


1365 


1690 


2330 


1000000 


W 


650 


55.2 

1 


740 


1215 


1460 


1840 


2520 



338 ELECTRICAL TABLES AND DATA 

Table CXXXIV 
Open Wires 
Table of Carrying Capacities; open wires. 
20° C; 36° F. temperature rise above surrounding air. 
Use this table for rubber covered wires where tempera- 
ture does not exceed 85° F., and for "Other insulations" 
where temperature is between 85° F. and 125° F. 





N. E. 


CODE 


Calculated Carrying Capacities 36 


F. rise 


B& S. 


£58 1 


14 


£ 2 1 




Short time 


in minutes 


gauge 


I'll 
III 


•05*^ 
























oo* 


a 




30 


15 


10 


5 


14 


20 


21.6 


25 


25 


29 


33 


37 


12 


25 


19.1 


31 


31 


39 


42 


47 


10 


30 


18.0 


41 


41 


47 


53 


60 


8 


50 


27.9 


52 


52 


60 


66 


75 


6 


70 


29.5 


67 


67 


80 


87 


95 


5 


80 




80 


80 


90 


100 


112 


4 


90 


32.6 


90 


90 


105 


120 


137 


3 


100 


26.1 


100 


100 


125 


145 


168 


2 


125 


30.6 


120 


120 


150 


175 


210 


1 


150 


32.4 


140 


145 


180 


220 


265 





200 


40.0 


160 


165 


215 


260 


330 


2/0 


225 


41.2 


186 


210 


250 


310 


380 


3/0 


275 


45.7 


215 


250 


300 


380 


465 


200000 


300 




240 


290 


345 


440 


535 


4/0 


325 


56.6 


250 


300 


360 


450 


560 


250000 


350 




285 


335 


410 


520 


660 


300000 


400 


38.6 


325 


400 


475 


620 


765 


350000 


450 




360 


450 


545 


700 


895 


400000 


500 


4*7^6 


400 


500 


600 


790 


1020 


500000 


600 


51.4 


480 


600 


730 


950 


1220 


600000 


680 




560 


690 


860 


1110 


1565 


700000 


760 




625 


775 


970 


1260 


1785 


750000 


800 


57.6 


650 


800 


1025 


1340 


1910 


800000 


840 




680 


850 


1090 


1400 


2040 


900000 


920 




730 


930 


1190 


1550 


2300 


1000000 


1000 


54.6 


775 


1000 


1285 


1665 


2500 



ELECTRICAL TABLES AND DATA 



332 



Table CXXXV 
Open Wires 
Table of Carrying Capacities; open wires. 
40° C; 72° F. temperature rise above surrounding air. 
Use this table for "Other insulations" where temperature 
does not exceed 80° F., and for rubber covered wires where 
temperature does not exceed 50° F. 





N. E. 


CODE 




Calculated 


Carrying Capacities 72 


° F. rise 


B&S. 


M£3 


i> 


■So" 




short time 


in minutes 


gauge 


fll 

33« 


si* 

a * 


l.gi 












30 


15 


10 


5 


14 


20 


21.6 


34 


34 


40 


46 


52 


12 


25 


19.1 


43 


43 


54 


59 


65 


10 


30 


18.0 


57 


57 


67 


74 


83 


8 


50 


27.9 


72 


72 


84 


92 


103 


6 


70 


29.5 


94 


94 


109 


122 


134 


5 


80 




110 


110 


127 


141 


157 


4 


90 


32.0 


125 


125 


145 


165 


190 


3 


100 


26.1 


145 


i45 


175 


202 


234 


2 


125 


30.6 


168 


170 


205 


245 


295 


1 


150 


32.4 


195 


205 


250 


309 


372 





200 


40.0 


225 


235 


300 


360 


460 


2/0 


225 


41.2 


260 


290 


350 


430 


530 


3/0 


275 


45.7 


300 


345 


410 


520 


645 


200000 


300 




335 


400 


480 


610 


750 


4/0 


325 


56.0 


350 


410 


500 


630 


785 


250000 


350 




400 


470 


575 


730 


9<>5 


300000 


400 


38.0 


450 


550 


660 


860 


1070 


350000 


450 




500 


630 


760 


980 


1250 


400000 


500 


47.0 


560 


700 


840 


1100 


1425 


500000 


600 


51.4 


670 


840 


1025 


1330 


1785 


600000 


680 




780 


965 


1200 


1550 


2190 


700000 


760 




870 


1080 


1370 


1760 


2500 


750000 


800 


57.6 


910 


1110 


1435 


1860 


2675 


800000 


840 




950 


1190 


1525 


1960 


2855 


900000 


920 




1020 


1300 


1665 


2150 


3215 


1000000 


1000 


54.6 


1085 


1400 


1800 


2330 


3500 



ELECTRICAL TABLES AND DATA 







Table CXXXVI 








Wires in 


Conduit 




Limiting 
Outer | 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range in 
Conduit 
F. 
22-27 


3 No. 14 TV ires in 
Heating load 
15 20 25 
2280 250 110 


y 2 " Conduit 
amperes 
45 
15 


Cooling Load; 
Amperes 
7% 
300 180 


118 88 


27-32 




300 


120 


15 


210 130 


113 83 


32-37 




450 


160 


15 


195 100 


108 78 


37-42 




660 


180 


15 


125 80 


103 73 


42-47 




1560 


210 


15 


95 70 


98 68 


47-52 






220 


15 


80 60 


93 63 


52-57 






350 


15 


60 60 


88 58 


57-62 






400 


15 


40 40 


83 53 


62-67 






540 


15 


40 40 


78 48 


67-72 






1350 


15 


40 40 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins: Ins. 

123 93 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


3 No. 12 "Wires in 
Heating load 
20 25 35 
840 200 50 


%" Conduit Cooling Load; 
amperes Amperes 
60 10 

13 230 200 


118 88 


27-32 




270 


50 


13 


200 150 


113 83 


32-37 




500 


60 


13 


170 100 


108 78 


37-42 




660 


80 


13 


120 100 


103 73 


42-47 




2000 


100 


13 


100 100 


98 68 


47-52 






100 


13 


100 90 


93 63 


52-57 






120 


13 


80 80 


88 58 


57-62 






200 


13 


50 50 


83 53 


62-67 






200 


13 


50 50 


78 48 


67-72 






220 


13 


50 50 


Limiting 
Outer 
Temp. 
Oth- Rub- 
er ber 
Ins. Ins. 
123 93 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


3 No. 10 Wires in 
Heating load 
25 35 50 

1380 210 60 


%" Conduit 
amperes 

75 

21 


Cooling Load; 
Amperes 
12i/ 2 
360 270 


118 88 


27-32 




210 


60 


21 


250 225 


113 83 


32-37 




270 


65 


21 


200 150 


108 78 


37-42 




300 


70 


21 


150 130 


103 73 


42-47 




540 


75 


21 


90 115 


98 68 


47-52 




1440 


80 


21 


90 85 


93 63 


52-57 






90 


21 


90 75 


88 58 


57-62 






120 


21 


90 75 


83 53 


62-57 






140 


21 


90 75 


83 53 


62-67 






140 


21 


90 75 


78 48 


67-72 






160 


21 


90 75 



ELECTRICAL TABLES AND DATA 



Limiting 
Outer 
Temp. 
Oth- Rub- 
er ber 
Ins. Ins. 
123 93 
118 88 
113 83 
108 78 
103 73 
98 68 
93 63 
88 58 
83 53 
78 48 

limiting 
Outer 
Temp. 
Oth- Rub- 
er ber 
Ins. Ins. 
123 93 
118 88 
113 83 
108 78 
103 73 
98 68 
93 63 
88 58 
83 53 
78 48 

Limiting 
Outer 
Temp. 
Oth- Rub- 
er ber 
Ins. Ins. 
123 93 
118 88 
113 83 
108 78 
103 73 



93 63 

88 58 

83 53 

78 48 



22-27 
27-32 
32-37 
37-42 
42-47 
47-52 
52-57 
57-62 
62-67 
67-72 

Temper- 
ature 

Range in 
Conduit 

F. 
22-27 
27-32 
32-37 
37-42 
42-47 
47-52 
52-57 
57-62 
62-67 
67-72 

Temper- 
ature 
Range in 
Conduit 
F. 

22-27 

27-32 
32-37 
37-42 
42-47 
<±7-52 
52-57 
57-62 
62-67 
67-72 



Table CXXXVII 
Wires in Conduit 



3 No. 8 Wires in Conduit 
Heating load; amperes 
105 



1380 210 
240 
270 
350 
540 



70 

60 
60 
70 
80 
90 



900 100 

1360 105 

110 

115 

120 



21 
21 
21 
21 
21 
21 
21 
21 
21 
21 



3 No. 6 Wires in Conduit 
Heating load; amperes 
100 150 



50 70 80 

1000 120 100 

1920 180 100 

200 100 

220 120 

300 140 

360 160 

450 180 

630 220 

840 240 

1260 260 



45 19 

50 19 

60 19 

80 19 

80 19 

90 19 

90 19 

90 19 

90 19 

£0 19 



Cooling Load; 
Amperes 
17% 

510 420 

345 290 

285 210 

240 160 

180 120 

120 100 

100 100 

90 

90 

90 



90 
90 
90 



Cooling Load; 
Amperes 
25 

600 330 

420 240 

300 225 

220 200 

180 120 

120 100 

100 100 

100 100 

100 100 

100 100 



3 No. 4 Wires in Conduit 

Heating load; amperes 

70 80 90 100 140 

600 360 240 135 50 

900 450 270 150 50 

1260 510 300 160 60 

2400 630, 390 200 70 

1080 480 240 70 

600 360 70 

950 450 75 

1800 510 75 

570 75 

780 80 



Cooling Load; 
Amperes 

210 35 

22 720 300 

22 480 270 

22 480 210 

22 320 150 

22 220 120 

22 180 110 

22 150 90 

22 130 80 

22 130 60 

22 130 60 



ELECTRICAL TABLES AND DATA 







Table CX 


XXV] 


[II 












Wires in 


Conduit 








Limiting 
Outer 
Temp. 
Oth- Rub- 
er ber 
Ins. Ins. 
123 93 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


3 No. 3 Wires in 
Heating load, 
80 90 100 
780 480 240 


1 \i " Conduit 
amperes 
160 240 

60 28 


Cooling Load; 
Amperes 
40 
600 420 


118 88 


27-32 


1500 


645 


300 


60 


28 


400 


300 


113 83 


32-37 




900 


400 


70 


28 


330 


175 


108 78 


37-42 




1300 


570 


72 


28 


300 


100 


103 73 


42-47 






780 


74 


28 


250 


100 


98 68 


47-52 








76 


28 


240 


100 


93 63 


52-57 








80 


28 


200 


75 


88 58 


57-62 








85 


28 


150 


75 


83 53 » 


62-67 








85 


28 


150 


75 


78 48 


67-72 








85 


28 


150 


75 


Limiting 
Outer 
Temp. 
Oth- Rub- 
er .ber 
Ins. Ins. 
123 93 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


3 No. 2 Wires in 
Heating load 
90 125 180 
840 240 65 


1%" Conduit 
amperes 
270 
25 


Cooling Load; 
Amperes 
45 

660 480 


118 88 


27-32 


1560 


260 


70 


25 




450 


350 


113 83 


32-37 




320 


75 


25 




345 


240 


108 78 


37-42 




360 


85 


25 




270 


200 


103 73 


42-47 




570 


95 


25 




165 


150 


98 68 


47-52 




720 


95 


25 




155 


110 


93 63 


52-57 




1000 


95 


25 




155 


110 


88 58 


57-62 




1900 


95 


25 




155 


110 


83 53 


62-67 






100 


25 




155 


110 


78 48 


67-72 






100 


25 




155 


100 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


3 No. 1 Wires in 1%" Conduit 
Heating load; amperes 
100 125 150 200 300 

840 310 170 90 29 


Cooling Load; 
Amperes 
50 
750 480 


118 88 


27-32 


1020 


330 


180 


90 


29 


580 


360 


113 83 


32-37 


1560 


420 


200 


100 


29 


420 


300 


108 78 


37-42 




600 


220 


100 


29 


360 


270 


103 73 


42-47 




810 


240 


110 


29 


270 


195 


98 68 


47-52 




1000 


270 


110 


29 


220 


165 


93 63 


52-57 




1560 


390 


125 


29 


180 


135 


88 58 


57-62 






450 


135 


29 


150 


135 


83 53 


62-67 






480 


135 


29 


150 


135 


78 48 


67-72 






720 


140 


29 


150 


135 



ELECTRICAL, TABLES AND DATA 







Table CXXXIX 








WlEES IN 


DONDUIT 




Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range in 

Conduit 

F. 

22-27 


3 No. Wires in Conduit 
Heating load; amperes 
125 175. 250 375 

550 190 85 32 


Cooling Load; 
Amperes 
62 y 2 
840 525 


118 88 


27-32 


800 


210 


85 


32 


600 390 


113 83 


32-37 


1140 


230 


85 


32 


480 -300 


108 78 


37-42 


2000 


250 


85 


32 


420 225 


103 73 


42-47 




300 


85 


32 


350 200 


98 68 


47-52 




400 


95 


32 


300 190 


93 63 


52-57 




480 


115 


32 


270 180 


88 58 


57-62 




540 


135 


32 


190 140 


83 53 


62-67 




700 


135 


32 


190 140 


78 48 


67-72 




1140 


135 


32 


190 140 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range in 

Conduit 

F. 

22-27 


3 No. 00 Wires 
Heating load; 
150 225 300 

700 180 60 


n Conduit 
amperes 
450 
31 


Cooling Load; 
Amperes 
75 
900 500 


118 88 


27-32 


960 


190 


60 


31 


720 360 


113 83 


32-37 


1680 


210 


60 


31 


570 330 


108 78 


37-42 


4000 


220 


90 


31 


435 315 


103 73 


42-47 




230 


90 


31 


360 240 


98 68 


47-52 




250 


90 


31 


250 210 


93 63 


52-57 




265 


105 


31 


195 160 


88 58 


57-62 




285 


105 


31 


160 130 


83 53 


62-67 




315 


105 


31 


160 130 


78 48 


67-72 




400 


105 


31 


160 130 


Limiting 
Outer- 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range in 

Conduit 

F. 

22-27 


3 No. 000 Wires in Conduit 
Heating load; amperes 
175 262% 350 525 

1100 200 100 38 


Cooling Load; 
Amperes 
87 V 2 
960 540 


118 88 


27-32 


1470 


210 


100 


38 


660 480 


113 83 


32-37 


2300 


220 


100 


38 


560 450 


108 78 


37-42 




240 


110 


38 


500 350 


103 73 


42-47 




270 


110 


38 


480 310 


98 68 


47-52 




300 


110 


38 


360 270 


93 63 


52-57 




360 


120 


38 


315 180 


88 58 


57-62 




420 


135 


38 


210 120 


83 53 


62-67 




480 


135 


38 


180 120 


78 48 


67-72 




660 


135 


38 


180 120 



ELECTRICAL TABLES AND DATA 







Table CXL 














Wires in 


Conduit 








Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range in 

Conduit 

F. 

22-27 


3 No. 200,000 C. M. Cables 

estimated i 
Heating load; amperes 
212 265 318 380 424 636 

420 180 135 100 72 29 


Cooling Load; 

Amperes 
106 

2040 660 


118 88 


27-32 


495 


220 


135 


100 


72 29 


1320 


540 


113 83 


32^37 


600 


240 


140 


100 


72 29 


780 


450 


108 78 


37-42 


780 


250 


140 


100 


72 29 


570 


300 


103 73 


42-47 


1200 


270 


150 


100 


72 29 


450 


300 


98 68 


47-52 


1980 


300 


150 


100 


72 29 


390 


240 


93 63 


52-57 


3300 


340 


165 


100 


72 29 


270 


180 


88 58 


57-62 




380 


165 


100 


72 29 


170 


150 


83 53 


62-67 




400 


240 


100 


72 29 


170 


150 


78 48 


67-72 




480 


240 


100 


72 29 


170 


150 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


3 No.400 Cables in 
Heating load 
225 281 337 

420 180 135 


2y 2 " Conduit Cooling Load; 
; amperes Amperes 
393 450 675 112y 2 

100 72 29 2040 660 


118 


27-32 


495 


220 


135 


100 


72 29 


1320 


540 


113 


32-37 


600 


240 


140 


100 


72 29 


780 


450 


108 


37-42 


780 


250 


140 


100 


72 29 


570 


300 


103 


42-47 


1200 


270 


150 


100 


72 29 


450 


300 


98 


47-52 


1980 


300 


150 


100 


72 29 


390 


240 


93 


52-57 


3300 


340 


165 


100 


72 29 


270 


180 


88 


57-62 




380 


165 


100 


72 29 


170 


150 


83 


62-67 




400 


240 


100 


72 29 


170 


150 


78 


67-72 




480 


240 


100 


72 29 


170 


150 


Limiting 
Outer 
Temp. 
Oth- Rub- 
er ber 
Ins. Ins. 
123 93 


Temper- 
ature 

Range in 

Conduit 

F. 

22-27 


S No. 250,000 C. M. Cables 

estimated Cooling Load; 
Heating load; amperes Amperes 
250 312 375 437 500 750 125 

420 180 135 100 72 29 2040 660 


118 88 


27-32 


495 


220 


135 


100 


72 29 


1320 


540 


113 83 


32-37 


600 


240 


140 


100 


72 29 


780 


450 


108 78 


37-42 


780 


250 


140 


100 


72 29 


570 


360 


103 73 


42-47 


1200 


270 


150 


100 


72 29 


450 


300 


98 68 


47-52 


1980 


300 


150 


100 


72 29 


390 


240 


93 63 


52-57 


3300 


340 


165 


100 


72 29 


270 


180 


88 58 


57-62 




380 


165 


100 


72 29 


170 


150 


83 53 


62-67 




400 


240 


100 


72 29 


170 


150 


78 48 


67-72 




480 


240 


100 


72 29 


170 


150 



ELECTRICAL TABLES AND DATA 







Table CXLI 














Wires in 


Conduit 








Limiting 
Outer 
Temp. 
Oth- Rub- 
er ber 
Ins. Ins. 
123 93 


Temper- 
ature 

Range in 

Conduit 

F. 

22-27 


3 No. 300,000 C. M. Cables 
in 3" Conduit 
Heating load; amperes 
275 343 412 550 825 

720 360 120 100 33 


Cooling Load; 
Amperes 
137 
1140 480 


118 88 


27-32 


840 


370 


150 


100 


33 


690 


400 


113 83 


32-37 


1320 


400 


160 


100 


33 


600 


360 


108 78 


37-42 


1980 


420 


170 


100 


33 


480 


260 


103 73 


42-47 




450 


180 


100 


33 


360 


240 


98 68 


47-52 




540 


190 


100 


33 


300 


220 


93 63 


52-57 




810 


250 


100 


33 


280 


180 


88 58 


57-62 




1080 


300 


100 


33 


210 


150 


83 53 


62-67 




2040 


350 


100 


33 


210 


150 


78 48 


67-72 






400 


100 


33 


210 


150 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range in 
Conduit 
P. 

22-27 


3 No. 350,000 C. M. Cables 
in Conduit, estimated 
Heating load; amperes 
300 375 450 600 900 

840 370 165 105 40 


Cooling Load; 
Amperes 
150 

1070 600 


118 88 


27-32 


1000 


400 


185 


105 


40 


780 


485 


113 83 


32-37 


3000 


455 


200 


105 


40 


660 


435 


108 78 


37-42 




480 


210 


105 


40 


600 


370 


103 73 


42-47 




540 


225 


105 


40 


480' 


320 


98 68 


47-52 




630 


240 


105 


40 


400 


260 


93 63 


52-57 




825 


315 


105 


40 


315 


210 


88 58 


57-62 




1080 


350 


105 


40 


300 


200 


83 53 


62-67 




1900 


415 


105 


40 


250 


175 


78 48 


67-72 






470 


105 


40 


220 


165 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


3 No. 400,000 C. M. Cables 
in 3" Conduit 
Heating load; amperes 
325 406 487 650 975 

960 390 210 110 46 


Cooling Load;, 
Amperes 
162% 

990 720 


118 88 


27-32 


1170 


430 


225 


110 


46 


870 


570 


113 83 


32-37 


1800 


510 


235 


110 


46 


720 


510 


108 78 


37-42 


4000 


540 


250 


110 


46 


615 


480 


103 73 


42-47 




630 


265 


110 


46 


600 


400 


98 68 


47-52 




720 


290 


110 


46 


510 


300 


93 63 


52-57 




840 


330 


110 


46 


480 


270 


88 58 


57-62 




1080 


400 


110 


46 


330 


250 


83 53 


62-67 




1740 


480 


110 


46 


300 


200 


78 48 


67-72 




4000 


540 


110 


46 


240 


180 



346 



ELECTRICAL. TABLES AND DATA 



Limiting 

Outer 
Temp. 
Oth- Rub- 
ber 



Ins. 
123 
118 
113 
108 



Ins. 
93 
88 
83 
78 
103 73 
98 68 
93 63 
88 58 
83 53 
78 48 



Temper- 
ature 
Range in 
Conduit 
P. 

22-27 
27-32 
32-37 
37-42 
42-47 
47-52 
52-57 
57-62 
62-67 
67-72 



Table CXLII 
Wiees in Conduit 

3 No. 500,000 C. M. Cables 

in 3" Conduit C« 

Heating load; amperes 
400 500 600 700 800 1200 

1050 360 250 165 122 42 

1140 400 270 165 122 42 

1440 430 300 175 122 42 

1860 480 330 175 122 42 

2700 560 360 195 122 42 

650 390 195 122 42 

750 420 210 122 42 

870 450 210 122 42 

960 465 225 122 42 

1260 480 225 122 42 



oling Load; 

Amperes 

200 

3500 1080 

1620 950 

1200 720 

900 540 

870 450 

600 360 

500 300 

440 240 

280 160 

200 110 



Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 



118 
113 



88 
83 



108 78 

103 73 

98 68 

93 63 

88 58 

83 53 

78 48 



Temper- 
ature 

Range in 

Conduit 

F. 

22-27 
27-32 
32-37 
37-42 
42-47 
47-52 
52-57 
57-62 
62-67 
67-72 



450 
1000 
1110 
1440 
2340 
3500 



3 No. 600,000 C. M. Cables 

in Conduit, estimated 

Heating load; amperes 



562 

420 
450 
480 
580 
660 
720 
780 
1020 
1500 



675 

240 
250 
260 
270 
290 
320 
360 
410 
420 
430 



785 900 1350 

160 122 42 
160 122 42 
160 122 42 
160 122 42 
160 122 42 
160 122 42 
160 122 42 
160 122 42 
160 122 42 
160 122 42 



Cooling Load; 
Amperes 



230 

2280 

1500 

1150 

900 

750 

660 

600 

510 

420 

270 



o 

900 
720 
600 
500 
480 
420 
390 
360 
300 
250 



Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


ature 
Range in 
Conduit 

22-21 


3 No. 700,000 C. M. Cables 

in Conduit, estimated Cooling Load; 
Heating load; amperes Amperes 
505 630 757 880 1010 1515 253 

1000 420 240 160 130 45 2280 900 


118 


88 


27-32 


1110 


450 


250 


160 


130 45 


1500 


720 


113 


83 


32-37 


1440 


480 


260 


160 


130 45 


1150 


600 


108 


78 


37-42 


2340 


600 


270 


160 


130 45 


900 


500 


103 


73 


42-47 


3500 


660 


300 


160 


130 45 


750 


480 


98 


68 


47-52 




720 


340 


160 


130 45 


660 


420 


93 


63 


52-57 




780 


380 


160 


130 45 


600 


390 


88 


58 


57-62 




1020 


420 


160 


130 45 


510 


360 


83 


53 


62-67 




1500 


460 


160 


130 45 


420 


300 


78 


48 


67-72 






500 


160 


130 45 


270 


250 



ELECTRICAL. TABLES AND DATA 



347 









Table CXLIII 














Wires in 


Conduit 








Limiting 
Outer 
Temp. 

Oth- Rub- 
er" ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


3 No. 750,000 C. M. Cables 
in 4" Conduit 
Heating load; amperes 
525 656 787 1050 1575 

900 420 230 150 54 


Cooling Load; 
Amperes 
262y 2 

2280 900 


118 


88 


27-32 


1110 450 


240 


150 


54 


1500 


720 


113 


83 


32-37 


1440 480 


250 


150 


54 


1150 


600 


108 


78 


37-42 


2340 570 


270 


150 


54 


900 


500 


103 


73 


42-47 


3500 660 


300 


150 


54 


750 


460 


98 


68 


47-52 


720 


340 


150 


54 


660 


420 


93 


63 


52-57 


780 


370 


150 


54 


600 


390 


88 


58 


57-62 


1020 


410 


150 


54- 


510 


360 


83 


53 


62-67 


1500 


450 


150 


54 


420 


300 


78 


48 


67-72 




500 


150 


54 


270 


250 


Limiting 

Outer 

Temp. 
Oth- Rub- 
er ber 
Ins. Ins. 
123 93 


Temper- 
ature 

Range in 
Conduit 

F. 
22-27 


3 No. 800,000 C. M. Cables 
in Conduit, estimated 
Heating load; amperes 
550 688 825 1100 1650 

900 420 230 150 54 


Cooling Load; 
Amperes 

275 
2280 900 


118 


88 


27-32 


1110 450 


240 


150 


54 


1500 


720 


113 


83 


32-37 


1440 480 


250 


150 


54 


1150 


600 


108 


78 


37-42 


2340 570 


270 


150 


54 


900 


500 


103 


73 


42-47 


3500 660 


300 


150 


54 


750 


460 


98 


68 


47-52 


720 


340 


150 


54 


660 


420 


93 


63 


52-57 


780 


370 


150 


54 


,600 


390 


88 


58 


57-62 


1020 


410 


150 


54 


510 


360 


83 


53 


62-67 


1500 


450 


150 


54 


420 


300 


78 


48 


67-72 




500 


150 


54 


270 


250 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


3 No. 900,000 C. M. Cables 
in Conduit, estimated 
Heating load; amperes 
600 750 900 1200 1800 

920 420 250 100 50 


Cooling Load; 
Amperes 

300 
2500 930 


118 


88 


27-32 


1020 465 


260 


100 


50 


1560 


780 


113 


83 


"32-37 


1200 480 


270 


100 


50 


1320 


720 


108 


78 


37-42 


1350 500 


280 


100 


50 


1050 


660 


103 


73 


42-47 


2250 530 


290 


100 


50 


870 


600 


98 


68 


47-52 


550 


300 


100 


50 


780 


540 


93 


63 


52-57 


600 


330 


100 


50 


670 


485 


88 


58 


57-62 


690 


345 


100 


50 


600 


450 


83 


53 


62-67 


960 


370 


100 


50 


400 


360 


78 


48 


67-72 


1400 


450 


100 


50 


330 


300 



348 



ELECTRICAL. TABLES AND DATA 







Table CXLIV 












Wires in 


Conduit 








Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 


Temper- 
ature 
Range in 
Conduit 
F. 


3 No 

650 


. 1,000,000 C. M. Cables 

in 4 y 2 " Conduit 
Heating load; amperes 
812 975 1300 1950 


Cooling Load; 
Amperes 
325 


123 93 


22-27 


930 


420 


250 100 


50 


2500 


930 


118 88 


27-32 


1020 


465 


260 100 


50 


1560 


780 


113 83 


32-37 


1200 


480 


270 100 


50 


1320 


720 


108 78 


37-42 


1350 


500 


280 100 


50 


1050 


660 


103 73 


42-47 


2250 


530 


290 100 


50 


870 


600 


98 68 


47-52 




550 


300 100 


50 


780 


540 


93 63 


52-57 




600 


330 100 


50 


670 


485 


88 58 


57*62 




690 


345 100 


50 


600 


450 


83 53 


62-67 




960 


385 100 


50 


400- 


360 


78 48 


67-72 




1400 


450 100 


50 


330 


300 



ELECTRICAL, TABLES AND DATA 



349^ 







Table ( 


:XL^ 










Open Wires 






Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 

Wire 

F. 

22-27 


No. 14 D. B. R. C. 

Heating load 
15 20 25 
120 


Wire in Air 
amperes 
45 
21 


Cooling Load; 
Amperes 

21 


118 88 


27-32 




390 


21 


21 


113 83 


32-37 






21 


21 


108 78 


37-42 






21 


21 


103 73 


42-47 






21 


21 


98 68 


47-52 






21 


21 


93 63 


52-57 






21 


21 


88 58 


57-62 






21 


21 


83 53 


62-67 






21 


2L 


78 48 


67-72 






21 




Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 
Wire 

F. 
22-27 


No. 12 D. B. R. C. 

Heating load 
20 25 35 

120 


Wire in Air 
; amperes 

60 

21 


Cooling Load; 
Amperes 

24 


118 88 


27-32 




150 


21 


24 


113 83 


32-37 




660 


21 


24 


108 78 


37-42 






21 


24 


103 73 


42-47 






21 


24 


98 68 


47-52 






21 


24 


93 63 


52-57 






21 


24 


88 58 


57-62 






21 


24 


83 53 


62-67 






21 


24 


78 48 


67-72 






21 


24 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 

Wire 

F 

22-27 


No. 10 D. B. R. C. 

Heating load 
25 35 50 
1020 80 


Wire in Air 
; amperes 

75 

32 


Cooling Load; 
Amperes 

21 


118 .88 


27-32 




90 


32 


21 


113 83 


32-37 




180 


32- - 


21 


108 78 


37-42 




300 


32 


21 


103 73 


42-47 






32 


21 


98 68 


47-52 






32 


21 


93 63 


52-57 


' 




32 


21 


88 58 


57-62 






32 


21. 


83 53 


62-67 






32 


21 


78 48 


67-72 






32 


21 



ELECTRICAL, TABLES AND DATA 







Table CXLVI 








i 


Open Wires 






limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range 
F. 

22-27 


No, 
35 


8 D. B. R. C. " 

Heating load 
50 70 
960 60 


Wire in Air < 
; amperes 
105 

23 


Pooling Load; 
Amperes 

40 


118 88 


27-32 




70 


23 


40 


113 83 


32-37 




85 


23 


40 


108 78 


37-42 




100 


23 


40 


103 73 


42-47 




180 


23 


40 


98 68 


47-52 




1350 


23 


40 


93 63 


52-57 






23 


40 


88 58 


57-62 






23 


40 


83 53 


62-67 






23 


40 


78 48 


67-72 






23 


40 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range 
F. 

22-27 


No 
50 


. 6 D. B. R. C. 

Heating load; 
70 80 
420 150 


Wire in Air 
; amperes 
100 
21 


Cooling Load; 

Amperes 


80 


118 88 


27-32 




240 


21 


70 


.113 83 


32-37 




650 


21 


60 


108 78 


37-42 






21 


50 


103 73 


42-47 






21 


40 


98 68 


47-52 






21 


30 


93 63 


52-57 






21 


30 


88 58 


57-62 






21 


30 


83 53 


62-67 






21 


30 


78 48 


67-72 






21 


30 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 
123 93 


Temper- 
ature 
Range 
F. 

22-27 


No. 
70 


4 D. B. R. C. Wire in Air Cooling Load; 
Heating load; amperes Amperes 
80 90 100 140 210 

420 200 60 17 85 


118 88 


27-32 




2000 


250 60 17 


80 


113 83 


32-37 






600 60 17 


75 


108 78 


37-42 






70 17 


70 


103 73 


42-47 






80 17 


60 


98 68 


47-52 






90 17 


50 


93 63 


52-57 






120 17 


40 


88 58 


57-62 






160 17 


40 


83 53 


62-67 






240 17 


40 


78 48 


67-72 






500 17 


40 



ELECTRICAL TABLES AND DATA 







Table CXLVII 










Open Wires 






Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 

Wire 

F. 

22-27 


No. 3 D. B. R. C. Wire in Air 

Heating load; amperes 
80 90 100 160 240 

1800 70 27 


Cooling Load; 
Amperes 

90 


118 88 


27-32 




75 


27 


80 


113 83 


32-37 




80 


27 


70 


108 78 


37-42 




85 


27 


60 


103 73 


42-47 




95 


27 


50 


98 68 


47-52 




120 


27 


40 


93 63 


52-57 




180 


27 


40 


88 58 


57-62 




300 


27 


40 


83 53 


62-67 




2000 


27 


40 


78 48 


67-72 






27 


40 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 

Wire 

P. 

22-27 


No. 2 D. B. R. C. Wire in Air 

Heating load; amperes 
90 125 180 270 

780 90 32 


Cooling Load; 
Amperes 
45 

130 100 


118 88 


27-32 




95 32 




90 80 


113 83 


32-37 




100 32 




80 60 


108 78 


37-42 




120 32 




60 40 


103 73 


42-47 




200 32 




52 40 


98 68 


47-£2 




330 32 




52 40 


93 63 


52-57 




540 32 




52 40 


88 58 


57-62 




32 




52 40 


83 53 


62-67 




32 




52 40 


78 48 


67-72 




32 




52 40 


Limiting 
Cuter 
Temp. ■ 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 
Wire 

F. 
22-27 


No. 1 D. B. R. C. Wire in Air 

Heating load; amperes 

100 125 150 200 300 

540 120 41 


Cooling Load; 
Amperes 
50 

150 100 


118 88 


27-32 




1300 150 


41 


100 70 


113 83 


32-37 




200 


41 


60 60 


108 78 


37-42 




250 


41 


60 60 


103 73 


42-47 




350 


41 


60 60 


98 68 


47-52 




500 


41 


60 60 


93 63 


52-57 




800 


41 


60 60 


88 58 


57-62 






41 


60 60 


83 53 


62-67 






41 


60 60 


78 48 


67-72 






41 


60 60 



352 



ELECTRICAL TABLES AND DATA 







Table CXLVII1 








Open Wires 






Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

ins. Ins. 

123 93 


Temper- 
ature 

Range of 

Wire 

F. 

22-27 


No. D. B. R. C. Cable in Air 

Heating load; amperes 
125 175 250 375 
2000 100 29 


Cooling Load; 
Amperes 
62V Z 

190 72 


118 88 


27-32 


105 


29 


150 72 


113 83 


32-37 


110 


29 


110 72 


108 78 


37-42 


115 


29 


100 72 


103 73 


42-47 


120 


29 


90 72 


98 68 


47-52 


180 


29 


80 72 


93 63 


52-57 


300 


29 


72 60 


88 58 


57-62 


500 


29 


72 60 


83 53 


62-67 


20U0 


29 


72 60 


78 48 


67-72 




29 


72 60 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 
Wire 

F. 
22-27 


No. 00 D. B. R. C. Cable in Air 
Heating load; amperes 
150 225 450 675 
375 100 38 


Cooling Load; 
Amperes 
75 
250 160 


118 88 


27-32 


500 100 


38 


210 140 


113 83 


32-37 


750 100 


38 


190 120 


108 78 


37-42 


1620 120 


38 


120 110 


103 73 


42-47 


140 


38 


70 80 


98 68 


47-52 


160 


38 


60 60 


93 63 


52-57 


180 


38 


60 60 


88 58 


57-62 


200 


38 


60 60 


83 53 


62-67 


230 


38 


60 60 


78 48 


67-72 


260 


38 


60 60 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 
Wire 

F. 
22-27 


No. 000 D. B. R. C. 

Heating load; 
175 262% 350 

390 85 


Cable in Air 
amperes 
525 

38 


Cooling Load; 
Amperes 
87Yz 
120 250 


118 88 


27-32 


465 85 


38 


120 165 


113 83 


32-37 


690 85 


38 


120 130 


108 78 


37-42 


2000 100 


38 


100 120 


103 73 


42-47 


125 


38 


90 110 


98 68 


47-52 


195 


38 


80 90 


93 63 


52-57 


300 


38 


80 80 


88 58 


57-62 


405 


38 


70 70 


83 53 


62-67 


600 


38 


70 70 


78 48 


67-72 


930 


38 


70 70 



ELECTRICAL. TABLES AND DATA 

Table CXLIX 
Open Wires 



Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 
123 93 


Temper- 
ature 

Range of 

Wire 

F. 

22-27 


No. 

210 


200,000 C. M. 

Heating load 

315 420 

195 75 


Wire in Air 
amperes 
630 
29 


Cooling Load; 
Amperes 

240 


118 88 


27-32 




195 


75 


29 


200 


113 83 


32-37 




195 


75 


29 


135 


108 78 


37-42 




195 


75 


29 


100 


103 73 


42-47 




240 


90 


29 


80 


98 68 


47-52 




300 


105 


29 


80 


93 63 


52-57 




400 


130 


29 


80 


88 58 


57-62 




540 


170 


29 


80 


83 53 


62-67 




1200 


200 


29 


80 


78 48 


67-72 






250 


29 


80 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 

Wire 

F. 

22-27 


No 
225 

2000 


. 0000 C. M. Cable in Air 
Heating load; amperes 
337 450 675 

195 75 29 


Cooling Load; 
Amperes 

240 


118 88 


27-32 




195 


75 


29 


200 


113 83 


32-37 




195 


75 


29 


135 


108 78 


37-42 




195 


75 


29 


100 


103 73 


42-47 




240 


90 


29 


80 


98 68 


47-52 




300 


105 


29 


80 


93 63 


52-57 




400 


130 


29 


80 


88 58 


57-62 




540 


170 


29 


80 


83 53 


62-67 




1200 


200 


29 


80 


78 48 


67-72 






250 


29 


80 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 

Wire 

F. 

22-27 


No 
250 


250,000 C. M. 

Heating load 

375 500 

200 100 


Cable in Air 
amperes 
750 
35 


Cooling Load; 
Amperes 

150 


118 88 


27-32 




200 


100 


35 


125 


113 83 


32-37 




220 


100 


35 


110 


108 78 


37-42 




250 


100 


35 


90 


103 73 


42-47 




300 


120 


35 


80 


98 68 


47-52 




400 


135 


35 


70 


93 63 


52-57 




500 


160 


35 


60 


88 58 


57-62 




800 


200 


35 


60 


83 53 


62-67 




1500 


300 


35 


60 


78 48 


67-72 






400 


55 


60 



ELECTRICAL. TABLES AND DATA 







Table CL 












Open Wires 








Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


No. 300,000 C. M. 
Heating load 
275 343 412 

1020 285 


Cable in Air 
amperes 
550 825 
125 42 


Cooling Load; 
Amperes 
137 
240 240 


118 88 


27-32 


4000 480 


135 


42 


210 210 


113 83 


32-37 


750 


150 


42 


150 150 


108 78 


37-42 


2300 


160 


42 


120 120 


103 73 


42-47 




180 


42 


100 100 


98 68 


47-52 




250 


42 


90 90 


93 63 


52-57 




275 


42 


80 80 


88 58 


57-62 




330 


42 


80 80 


83 53 


62-67 




375 


42 


80 80 


78 48 


67-72 




600 


42 


80 80 


Limiting 
Outer 
Temp. 
Oth- Rub- 
er ber 
Ins. Ins. 
123 93 


Temper- 
ature 

Range in 

Conduit 

F. 

22-27 


No. 350,000 C. M. 
Heating load 
300 375 450 
960 300 


Cable in Air 

amperes 
600 900 
110 46 


Cooling Load; 
Amperes 
150 
360 200 


118 88 


27-32 


3000 450 


120 


46 


240 150 


113 83 


32-37 


720 


130 


46 


180 80 


108 78 


37-42 


1200 


165 


46 


150 80 


103 73 


42-47 




185 


46 


80 80 


98 68 


47-52 




240 


46 


80 80 


93 63 


52-57 




290 


46 


80 80 


88 58 


57-62 




340 


46 


80 80 


83 53 


62-67 




420 


46 


80 80 


78 48 


67-72 




500 


46 


80 80 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


No. 400,000 C. M. 
Heating load 
325 408 487 
960 300 


Cable in Air 
amperes 
650 975 
110 46 


Cooling Load; 
Amperes 
162 
360 200 


118 88 


27-32 


3000 450 


120 


46 


240 150 


113 83 


32-37 


720 


130 


46 


180 80 


108 78 


37-42 


1200 


165 


46 


150 80 


103 73 


42-47 




185 


46 


80 80 


98 68 


47-52 




240 


46 


80 80 


93 63 


52-57 




290 


46 


80 80 


88 58 


57-62 




340 


46 


80 80 


83 53 


62-67 




420 


46 


80 80 


78 48 


67-72 




500 


46 


80 80 



ELECTRICAL TABLES AND DATA 







Table CLI 












Open Wires 








Limiting 

Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range in 
Conduit 
F. 

22-27 


No. 500,000 C. M. 
Heating load 
400 500 600 

690 345 


Cable in Air Cooling Load; 
amperes Amperes 
700 800 1200 

190 180 50 480 400 


118 88 


27-32 


1110 


480 


200 180 50 


300 


300 


113 83 


32-37 


4000 


750 


240 180 50 


200 


250 


108 78 


37-42 




900 


270 180 50 


125 


200 


103 73 


42-47 




1500 


300 180 50 


84 


150 


98 68 


47-52 






360 180 50 


84 


84 


93 63 


52-57 






540 180 50 


84 


84 


88 58 


57-62 






750 180 50 


84 


84 


83 53 


62-67 






180 50 


84 


84 


78 48 


67-72 






180 50 


84 


84 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 
Range in 
Conduit 

P. 
22-27 


No. 600,000 C. M. 
Heating load 
450 560 675 

700 360 


Cable in Air Cooling Load ; 
amperes Amperes 
786 900 1350 225 

200 185 52 480 400 


118 88 


27-32 


1200 


500 


210 185 52 


300 


300 J 


113 83 


32-37 




775 


250 185 52 


200 


250 I 


108 78 


37-42 




950 


280 185 52 


125 


200 


103 73 


42-47 




1600 


310 185 52 


84 


150 


98 68 


47-52 






370 185 52 


84 


84 


93 63 


52-57 






550 185 52 


84 


84 


88 58 


57-62 






775 185 52 


84 


84 


83 53 


62-67 






185 52 


84 


84 


78 48 


67-72 






185 52 


84 


84 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range in 
Conduit 

F. 
22-27 


No. 700,000 C. M. 
Heating load 
500 625 750 
660 270 


Cables in Air Cooling Load; 
■ amperes Amperes 
1000 1500 262 
150 53 660 400 


118 88 


27-32 


840 


300 


160 53 


450 


300 


113 83 


32-37 


1410 


375 


170 53 


400 


250 


lOo 78 


37-42 




500 


180 53 


270 


220 


103 73 


42-47 




625 


195 53 


220 


200 


98 68 


47-52 




775 


210 53 


200 


200 


93 63 


52-57 




1200 


240 53 


150 


150 


88 58 


57-62 






260 53 


150 


150 


83 53 


62-67 






280 53 


150 


150 


78 48 


67-72 






300 53 


150 


150 . 



356 



ELECTRICALi TABLES AND DATA 









Table CLI] 
















Open Wires 










Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 

Wire 

F. 

22-27 


No. 750,000 C. M 
Heating load 
525 656 787 
660 270 


. Cable in Air 
.; amperes 
1050 1575 
150 54 


Cooling Load; 
Amperes 
262 
660 400 


118 


88 


27-32 


840 


300 


160 


54 


450 


300 


113 


83 


32-37 


1410 


375 


170 


54 


400 


250 


108 


x78 


37-42 




500 


180 


54 


270 


220 


103 


73 


42-47 




625 


195 


54 


220 


200 


98 


68 


47-52 




775 


210 


54 


200 


200 


93 


63 


52-57 




1200 


240 


54 


150 


150 


88 


58 


57-62 






260 


54 


150 


150 


83 


53 


62-67 






280 


54 


150 


150 


78 


48 


67-72 






300 


54 


150 


150 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 
Wire 

F. 
22-27 


No. 800,000 C. M. 
Heating load 
550 687 825 

660 270 


Cable in Air 
; amperes 
1100 1650 
150 56 


Cooling Load; 
Amperes 
275 
660 400 


118 


88 


27-32 


840 


300 


160 


56 


450 


300 


113 


83 


32-37 


1410 


275 


170 


56 


400 


250 


108 


78 


37-42 




500 


180 


56 


270 


220 


103 


73 


42-47 




625 


195 


56 


220 


200 


98 


68 


47-52 




775 


210 


56 


200 


200 


93 


63 


52-57 




1200 


240 


56 


150 


150 


88 


58 


57-62 






260 


56 


150- 


150 


83 


53 


62-67 






280 


56 


150 


150 


78 


48 


67-72 






300 


56 


150 


150 


Limiting 
Outer 
Temp. 

Oth- Rub- 
er . ber 

Ins. Ins. 

123 93 


Temper- 
ature 

Range of 
Wire 

F. 
22-27 


No. 900,000 C. M. 
Heating load 
600 750 900 

720 330 


Cable in Air 
; amperes 
1200 1800 
120 58 


Cooling Load; 
Amperes 
300 ' 
660 480 


118 


88 


27-32 


1035 


400 


130 


58 


500 


320 


113 


83 


32-37 


2400 


525 


140 


58 


I 420 


275 


108 


78 


37-42 




630 


150 


58 


300 


200 


103 


73 


42-47 




800 


160 


58 


250 


175 


98 


68 


47-52 




1100 


170 


58 


200 


175 


93 


63 


52-57 






180 


58 


175 


175 


88 


58 


57-62 






200 


58 


175 


175 


83 


53 


62-67 






220 


58 


175 


175 


78 


48 


67-72 






250 


58 


175 


175 



ELECTRICAL TABLES AND DATA 





\ 


Table CLIII 














Open Wires 










Limiting 
Outer 
Temp. 

Oth- Rub- 
er ber 

Ins. Ins. 


Temper- 
ature 
Range in 
Conduit 
F. 


No. l.OOO.OOOC. M 
Heating load 
650 812 975 


Cable in Air 
amperes 
1300 1950 


Cooling L.oad; 
Amperes 
325 


123 93 


22-27 


720 330 


120 


58 


660 


480 


118 88 


27-32 


1035 400 


130 


58 


500 


320 


113 83 


32-37 


2400 525 


140 


58 


420 


275 


108 78 


37-42 


630 


150 


58 


300 


200 


103 73 


42-47 


800 


160 


58 


250 


175 


98 68 


47-52 


1100 


170 


58 


200 


175 


93 63 


52-57 




180 


58 


175 


175 


88 58 


57-62 




200 


58 


175 


175 


83 53 


62-67 




220 


58 


175 


175 


78 48 


67-72 




250 


58 


175 


175 



INDEX TO TABLES 

PAGE 

Aluminum and copper wire comparison 8 

Are lamp data 10 

Armored cable data 11 

Belting data 19 to 23 

Bus bar data 27 

Centigrade and Fahrenheit comparison 32 to 33 

Center of distribution data 30 

Conduit size recommendations 35 to 37 

Conversion, inch to decimals 329 

Cutout locations 25 

Cutout dimensions | 44 to 47 

Electrolysis 57 to 58 . 

Economy of conductors 309 to 310 

Economy of motors . 163 to 164 

Elevator H. P. requirements 67 

Fusing currents . 80 

Fusing transformers '. 77 

Fuse wire 78 to 79 

Gauges, comparison of 82 to 83 

Guying 172 

Heating 97 to 100 

Illumination' 105 to 114 

Insulator dimensions 118 to 121 

Lamp renewals 117 

Logarithms 126 

Machinery, power determination for 160 

Magnet calculations 61 to 65 

Melting points 131 

Meters, maximum demand 140 

Motor speeds, a. c 145 

Motor wiring tables... 287 to 293 

Nails, dimensions of 165 

Overhead const, data 170 to 175 

Panel board dimensions 178 to 180 

Pumping 183 to 185 

Reciprocals of numbers 187 to 190 

Reflectors 191 

358 



ELECTBICAL TABLES AND DATA 359 

PAGE 

Ropes 200 to 201 

Screw data 205 

Sign hanging 208 to 210 

Sign letters 207 

Sparking distances 215 

Switches, dimensions of 224 to 231 

Terminals, dimensions of 237 to 238 

Transformer distribution 256 

Transformer efficiency 258 

Trollev losses 260 

Ventilation 271 to 274 

Wires, aluminum 316 to 321 

" calculations 285 to 309 

" carrying capacity N. E. C 282 

" " " combined 284 

" " " underground 265 to 268 

«« " " for snort periods 330 to 357 

" copper 311 to 315 

' ' copper clad 322 to 323 

' ' German silver 324 

' ' mains and branches 222 

' ' outside dimensions of 326 to 328 

' ' quantity required 218 

" reactances and resistances 278, 297 to 299 

* ' sag and breaking strain 170 

' * telegraph and telephone 325 



